1PERLDIAG(1)            Perl Programmers Reference Guide            PERLDIAG(1)
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NAME

6       perldiag - various Perl diagnostics
7

DESCRIPTION

9       These messages are classified as follows (listed in increasing order of
10       desperation):
11
12           (W) A warning (optional).
13           (D) A deprecation (enabled by default).
14           (S) A severe warning (enabled by default).
15           (F) A fatal error (trappable).
16           (P) An internal error you should never see (trappable).
17           (X) A very fatal error (nontrappable).
18           (A) An alien error message (not generated by Perl).
19
20       The majority of messages from the first three classifications above (W,
21       D & S) can be controlled using the "warnings" pragma.
22
23       If a message can be controlled by the "warnings" pragma, its warning
24       category is included with the classification letter in the description
25       below.  E.g. "(W closed)" means a warning in the "closed" category.
26
27       Optional warnings are enabled by using the "warnings" pragma or the -w
28       and -W switches.  Warnings may be captured by setting $SIG{__WARN__} to
29       a reference to a routine that will be called on each warning instead of
30       printing it.  See perlvar.
31
32       Severe warnings are always enabled, unless they are explicitly disabled
33       with the "warnings" pragma or the -X switch.
34
35       Trappable errors may be trapped using the eval operator.  See "eval" in
36       perlfunc.  In almost all cases, warnings may be selectively disabled or
37       promoted to fatal errors using the "warnings" pragma.  See warnings.
38
39       The messages are in alphabetical order, without regard to upper or
40       lower-case.  Some of these messages are generic.  Spots that vary are
41       denoted with a %s or other printf-style escape.  These escapes are
42       ignored by the alphabetical order, as are all characters other than
43       letters.  To look up your message, just ignore anything that is not a
44       letter.
45
46       accept() on closed socket %s
47           (W closed) You tried to do an accept on a closed socket.  Did you
48           forget to check the return value of your socket() call?  See
49           "accept" in perlfunc.
50
51       Aliasing via reference is experimental
52           (S experimental::refaliasing) This warning is emitted if you use a
53           reference constructor on the left-hand side of an assignment to
54           alias one variable to another.  Simply suppress the warning if you
55           want to use the feature, but know that in doing so you are taking
56           the risk of using an experimental feature which may change or be
57           removed in a future Perl version:
58
59               no warnings "experimental::refaliasing";
60               use feature "refaliasing";
61               \$x = \$y;
62
63       Allocation too large: %x
64           (X) You can't allocate more than 64K on an MS-DOS machine.
65
66       '%c' allowed only after types %s in %s
67           (F) The modifiers '!', '<' and '>' are allowed in pack() or
68           unpack() only after certain types.  See "pack" in perlfunc.
69
70       alpha->numify() is lossy
71           (W numeric) An alpha version can not be numified without losing
72           information.
73
74       Ambiguous call resolved as CORE::%s(), qualify as such or use &
75           (W ambiguous) A subroutine you have declared has the same name as a
76           Perl keyword, and you have used the name without qualification for
77           calling one or the other.  Perl decided to call the builtin because
78           the subroutine is not imported.
79
80           To force interpretation as a subroutine call, either put an
81           ampersand before the subroutine name, or qualify the name with its
82           package.  Alternatively, you can import the subroutine (or pretend
83           that it's imported with the "use subs" pragma).
84
85           To silently interpret it as the Perl operator, use the "CORE::"
86           prefix on the operator (e.g. "CORE::log($x)") or declare the
87           subroutine to be an object method (see "Subroutine Attributes" in
88           perlsub or attributes).
89
90       Ambiguous range in transliteration operator
91           (F) You wrote something like "tr/a-z-0//" which doesn't mean
92           anything at all.  To include a "-" character in a transliteration,
93           put it either first or last.  (In the past, "tr/a-z-0//" was
94           synonymous with "tr/a-y//", which was probably not what you would
95           have expected.)
96
97       Ambiguous use of %s resolved as %s
98           (S ambiguous) You said something that may not be interpreted the
99           way you thought.  Normally it's pretty easy to disambiguate it by
100           supplying a missing quote, operator, parenthesis pair or
101           declaration.
102
103       Ambiguous use of -%s resolved as -&%s()
104           (S ambiguous) You wrote something like "-foo", which might be the
105           string "-foo", or a call to the function "foo", negated.  If you
106           meant the string, just write "-foo".  If you meant the function
107           call, write "-foo()".
108
109       Ambiguous use of %c resolved as operator %c
110           (S ambiguous) "%", "&", and "*" are both infix operators (modulus,
111           bitwise and, and multiplication) and initial special characters
112           (denoting hashes, subroutines and typeglobs), and you said
113           something like "*foo * foo" that might be interpreted as either of
114           them.  We assumed you meant the infix operator, but please try to
115           make it more clear -- in the example given, you might write "*foo *
116           foo()" if you really meant to multiply a glob by the result of
117           calling a function.
118
119       Ambiguous use of %c{%s} resolved to %c%s
120           (W ambiguous) You wrote something like "@{foo}", which might be
121           asking for the variable @foo, or it might be calling a function
122           named foo, and dereferencing it as an array reference.  If you
123           wanted the variable, you can just write @foo.  If you wanted to
124           call the function, write "@{foo()}" ... or you could just not have
125           a variable and a function with the same name, and save yourself a
126           lot of trouble.
127
128       Ambiguous use of %c{%s[...]} resolved to %c%s[...]
129       Ambiguous use of %c{%s{...}} resolved to %c%s{...}
130           (W ambiguous) You wrote something like "${foo[2]}" (where foo
131           represents the name of a Perl keyword), which might be looking for
132           element number 2 of the array named @foo, in which case please
133           write $foo[2], or you might have meant to pass an anonymous
134           arrayref to the function named foo, and then do a scalar deref on
135           the value it returns.  If you meant that, write "${foo([2])}".
136
137           In regular expressions, the "${foo[2]}" syntax is sometimes
138           necessary to disambiguate between array subscripts and character
139           classes.  "/$length[2345]/", for instance, will be interpreted as
140           $length followed by the character class "[2345]".  If an array
141           subscript is what you want, you can avoid the warning by changing
142           "/${length[2345]}/" to the unsightly "/${\$length[2345]}/", by
143           renaming your array to something that does not coincide with a
144           built-in keyword, or by simply turning off warnings with "no
145           warnings 'ambiguous';".
146
147       '|' and '<' may not both be specified on command line
148           (F) An error peculiar to VMS.  Perl does its own command line
149           redirection, and found that STDIN was a pipe, and that you also
150           tried to redirect STDIN using '<'.  Only one STDIN stream to a
151           customer, please.
152
153       '|' and '>' may not both be specified on command line
154           (F) An error peculiar to VMS.  Perl does its own command line
155           redirection, and thinks you tried to redirect stdout both to a file
156           and into a pipe to another command.  You need to choose one or the
157           other, though nothing's stopping you from piping into a program or
158           Perl script which 'splits' output into two streams, such as
159
160               open(OUT,">$ARGV[0]") or die "Can't write to $ARGV[0]: $!";
161               while (<STDIN>) {
162                   print;
163                   print OUT;
164               }
165               close OUT;
166
167       Applying %s to %s will act on scalar(%s)
168           (W misc) The pattern match ("//"), substitution ("s///"), and
169           transliteration ("tr///") operators work on scalar values.  If you
170           apply one of them to an array or a hash, it will convert the array
171           or hash to a scalar value (the length of an array, or the
172           population info of a hash) and then work on that scalar value.
173           This is probably not what you meant to do.  See "grep" in perlfunc
174           and "map" in perlfunc for alternatives.
175
176       Arg too short for msgsnd
177           (F) msgsnd() requires a string at least as long as sizeof(long).
178
179       Argument "%s" isn't numeric%s
180           (W numeric) The indicated string was fed as an argument to an
181           operator that expected a numeric value instead.  If you're
182           fortunate the message will identify which operator was so
183           unfortunate.
184
185           Note that for the "Inf" and "NaN" (infinity and not-a-number) the
186           definition of "numeric" is somewhat unusual: the strings themselves
187           (like "Inf") are considered numeric, and anything following them is
188           considered non-numeric.
189
190       Argument list not closed for PerlIO layer "%s"
191           (W layer) When pushing a layer with arguments onto the Perl I/O
192           system you forgot the ) that closes the argument list.  (Layers
193           take care of transforming data between external and internal
194           representations.)  Perl stopped parsing the layer list at this
195           point and did not attempt to push this layer.  If your program
196           didn't explicitly request the failing operation, it may be the
197           result of the value of the environment variable PERLIO.
198
199       Argument "%s" treated as 0 in increment (++)
200           (W numeric) The indicated string was fed as an argument to the "++"
201           operator which expects either a number or a string matching
202           "/^[a-zA-Z]*[0-9]*\z/".  See "Auto-increment and Auto-decrement" in
203           perlop for details.
204
205       Array passed to stat will be coerced to a scalar%s
206           (W syntax) You called stat() on an array, but the array will be
207           coerced to a scalar - the number of elements in the array.
208
209       A signature parameter must start with '$', '@' or '%'
210           (F) Each subroutine signature parameter declaration must start with
211           a valid sigil; for example:
212
213               sub foo ($a, $, $b = 1, @c) {}
214
215       A slurpy parameter may not have a default value
216           (F) Only scalar subroutine signature parameters may have a default
217           value; for example:
218
219               sub foo ($a = 1)        {} # legal
220               sub foo (@a = (1))      {} # invalid
221               sub foo (%a = (a => b)) {} # invalid
222
223       assertion botched: %s
224           (X) The malloc package that comes with Perl had an internal
225           failure.
226
227       Assertion %s failed: file "%s", line %d
228           (X) A general assertion failed.  The file in question must be
229           examined.
230
231       Assigned value is not a reference
232           (F) You tried to assign something that was not a reference to an
233           lvalue reference (e.g., "\$x = $y").  If you meant to make $x an
234           alias to $y, use "\$x = \$y".
235
236       Assigned value is not %s reference
237           (F) You tried to assign a reference to a reference constructor, but
238           the two references were not of the same type.  You cannot alias a
239           scalar to an array, or an array to a hash; the two types must
240           match.
241
242               \$x = \@y;  # error
243               \@x = \%y;  # error
244                $y = [];
245               \$x = $y;   # error; did you mean \$y?
246
247       Assigning non-zero to $[ is no longer possible
248           (F) When the "array_base" feature is disabled (e.g., and under "use
249           v5.16;", and as of Perl 5.30) the special variable $[, which is
250           deprecated, is now a fixed zero value.
251
252       Assignment to both a list and a scalar
253           (F) If you assign to a conditional operator, the 2nd and 3rd
254           arguments must either both be scalars or both be lists.  Otherwise
255           Perl won't know which context to supply to the right side.
256
257       Assuming NOT a POSIX class since %s in regex; marked by <-- HERE in
258       m/%s/
259           (W regexp) You had something like these:
260
261            [[:alnum]]
262            [[:digit:xyz]
263
264           They look like they might have been meant to be the POSIX classes
265           "[:alnum:]" or "[:digit:]".  If so, they should be written:
266
267            [[:alnum:]]
268            [[:digit:]xyz]
269
270           Since these aren't legal POSIX class specifications, but are legal
271           bracketed character classes, Perl treats them as the latter.  In
272           the first example, it matches the characters ":", "[", "a", "l",
273           "m", "n", and "u".
274
275           If these weren't meant to be POSIX classes, this warning message is
276           spurious, and can be suppressed by reordering things, such as
277
278            [[al:num]]
279
280           or
281
282            [[:munla]]
283
284       <> at require-statement should be quotes
285           (F) You wrote "require <file>" when you should have written
286           "require 'file'".
287
288       Attempt to access disallowed key '%s' in a restricted hash
289           (F) The failing code has attempted to get or set a key which is not
290           in the current set of allowed keys of a restricted hash.
291
292       Attempt to bless into a freed package
293           (F) You wrote "bless $foo" with one argument after somehow causing
294           the current package to be freed.  Perl cannot figure out what to
295           do, so it throws up its hands in despair.
296
297       Attempt to bless into a reference
298           (F) The CLASSNAME argument to the bless() operator is expected to
299           be the name of the package to bless the resulting object into.
300           You've supplied instead a reference to something: perhaps you wrote
301
302               bless $self, $proto;
303
304           when you intended
305
306               bless $self, ref($proto) || $proto;
307
308           If you actually want to bless into the stringified version of the
309           reference supplied, you need to stringify it yourself, for example
310           by:
311
312               bless $self, "$proto";
313
314       Attempt to clear deleted array
315           (S debugging) An array was assigned to when it was being freed.
316           Freed values are not supposed to be visible to Perl code.  This can
317           also happen if XS code calls "av_clear" from a custom magic
318           callback on the array.
319
320       Attempt to delete disallowed key '%s' from a restricted hash
321           (F) The failing code attempted to delete from a restricted hash a
322           key which is not in its key set.
323
324       Attempt to delete readonly key '%s' from a restricted hash
325           (F) The failing code attempted to delete a key whose value has been
326           declared readonly from a restricted hash.
327
328       Attempt to free non-arena SV: 0x%x
329           (S internal) All SV objects are supposed to be allocated from
330           arenas that will be garbage collected on exit.  An SV was
331           discovered to be outside any of those arenas.
332
333       Attempt to free nonexistent shared string '%s'%s
334           (S internal) Perl maintains a reference-counted internal table of
335           strings to optimize the storage and access of hash keys and other
336           strings.  This indicates someone tried to decrement the reference
337           count of a string that can no longer be found in the table.
338
339       Attempt to free temp prematurely: SV 0x%x
340           (S debugging) Mortalized values are supposed to be freed by the
341           free_tmps() routine.  This indicates that something else is freeing
342           the SV before the free_tmps() routine gets a chance, which means
343           that the free_tmps() routine will be freeing an unreferenced scalar
344           when it does try to free it.
345
346       Attempt to free unreferenced glob pointers
347           (S internal) The reference counts got screwed up on symbol aliases.
348
349       Attempt to free unreferenced scalar: SV 0x%x
350           (S internal) Perl went to decrement the reference count of a scalar
351           to see if it would go to 0, and discovered that it had already gone
352           to 0 earlier, and should have been freed, and in fact, probably was
353           freed.  This could indicate that SvREFCNT_dec() was called too many
354           times, or that SvREFCNT_inc() was called too few times, or that the
355           SV was mortalized when it shouldn't have been, or that memory has
356           been corrupted.
357
358       Attempt to pack pointer to temporary value
359           (W pack) You tried to pass a temporary value (like the result of a
360           function, or a computed expression) to the "p" pack() template.
361           This means the result contains a pointer to a location that could
362           become invalid anytime, even before the end of the current
363           statement.  Use literals or global values as arguments to the "p"
364           pack() template to avoid this warning.
365
366       Attempt to reload %s aborted.
367           (F) You tried to load a file with "use" or "require" that failed to
368           compile once already.  Perl will not try to compile this file again
369           unless you delete its entry from %INC.  See "require" in perlfunc
370           and "%INC" in perlvar.
371
372       Attempt to set length of freed array
373           (W misc) You tried to set the length of an array which has been
374           freed.  You can do this by storing a reference to the scalar
375           representing the last index of an array and later assigning through
376           that reference.  For example
377
378               $r = do {my @a; \$#a};
379               $$r = 503
380
381       Attempt to use reference as lvalue in substr
382           (W substr) You supplied a reference as the first argument to
383           substr() used as an lvalue, which is pretty strange.  Perhaps you
384           forgot to dereference it first.  See "substr" in perlfunc.
385
386       Attribute prototype(%s) discards earlier prototype attribute in same
387       sub
388           (W misc) A sub was declared as sub foo : prototype(A) :
389           prototype(B) {}, for example.  Since each sub can only have one
390           prototype, the earlier declaration(s) are discarded while the last
391           one is applied.
392
393       av_reify called on tied array
394           (S debugging) This indicates that something went wrong and Perl got
395           very confused about @_ or @DB::args being tied.
396
397       Bad arg length for %s, is %u, should be %d
398           (F) You passed a buffer of the wrong size to one of msgctl(),
399           semctl() or shmctl().  In C parlance, the correct sizes are,
400           respectively, sizeof(struct msqid_ds *), sizeof(struct semid_ds *),
401           and sizeof(struct shmid_ds *).
402
403       Bad evalled substitution pattern
404           (F) You've used the "/e" switch to evaluate the replacement for a
405           substitution, but perl found a syntax error in the code to
406           evaluate, most likely an unexpected right brace '}'.
407
408       Bad filehandle: %s
409           (F) A symbol was passed to something wanting a filehandle, but the
410           symbol has no filehandle associated with it.  Perhaps you didn't do
411           an open(), or did it in another package.
412
413       Bad free() ignored
414           (S malloc) An internal routine called free() on something that had
415           never been malloc()ed in the first place.  Mandatory, but can be
416           disabled by setting environment variable "PERL_BADFREE" to 0.
417
418           This message can be seen quite often with DB_File on systems with
419           "hard" dynamic linking, like "AIX" and "OS/2".  It is a bug of
420           "Berkeley DB" which is left unnoticed if "DB" uses forgiving system
421           malloc().
422
423       Bad hash
424           (P) One of the internal hash routines was passed a null HV pointer.
425
426       Badly placed ()'s
427           (A) You've accidentally run your script through csh instead of
428           Perl.  Check the #! line, or manually feed your script into Perl
429           yourself.
430
431       Bad name after %s
432           (F) You started to name a symbol by using a package prefix, and
433           then didn't finish the symbol.  In particular, you can't
434           interpolate outside of quotes, so
435
436               $var = 'myvar';
437               $sym = mypack::$var;
438
439           is not the same as
440
441               $var = 'myvar';
442               $sym = "mypack::$var";
443
444       Bad plugin affecting keyword '%s'
445           (F) An extension using the keyword plugin mechanism violated the
446           plugin API.
447
448       Bad realloc() ignored
449           (S malloc) An internal routine called realloc() on something that
450           had never been malloc()ed in the first place.  Mandatory, but can
451           be disabled by setting the environment variable "PERL_BADFREE" to
452           1.
453
454       Bad symbol for array
455           (P) An internal request asked to add an array entry to something
456           that wasn't a symbol table entry.
457
458       Bad symbol for dirhandle
459           (P) An internal request asked to add a dirhandle entry to something
460           that wasn't a symbol table entry.
461
462       Bad symbol for filehandle
463           (P) An internal request asked to add a filehandle entry to
464           something that wasn't a symbol table entry.
465
466       Bad symbol for hash
467           (P) An internal request asked to add a hash entry to something that
468           wasn't a symbol table entry.
469
470       Bad symbol for scalar
471           (P) An internal request asked to add a scalar entry to something
472           that wasn't a symbol table entry.
473
474       Bareword found in conditional
475           (W bareword) The compiler found a bareword where it expected a
476           conditional, which often indicates that an || or && was parsed as
477           part of the last argument of the previous construct, for example:
478
479               open FOO || die;
480
481           It may also indicate a misspelled constant that has been
482           interpreted as a bareword:
483
484               use constant TYPO => 1;
485               if (TYOP) { print "foo" }
486
487           The "strict" pragma is useful in avoiding such errors.
488
489       Bareword in require contains "%s"
490       Bareword in require maps to disallowed filename "%s"
491       Bareword in require maps to empty filename
492           (F) The bareword form of require has been invoked with a filename
493           which could not have been generated by a valid bareword permitted
494           by the parser.  You shouldn't be able to get this error from Perl
495           code, but XS code may throw it if it passes an invalid module name
496           to "Perl_load_module".
497
498       Bareword in require must not start with a double-colon: "%s"
499           (F) In "require Bare::Word", the bareword is not allowed to start
500           with a double-colon.  Write "require ::Foo::Bar" as  "require
501           Foo::Bar" instead.
502
503       Bareword "%s" not allowed while "strict subs" in use
504           (F) With "strict subs" in use, a bareword is only allowed as a
505           subroutine identifier, in curly brackets or to the left of the "=>"
506           symbol.  Perhaps you need to predeclare a subroutine?
507
508       Bareword "%s" refers to nonexistent package
509           (W bareword) You used a qualified bareword of the form "Foo::", but
510           the compiler saw no other uses of that namespace before that point.
511           Perhaps you need to predeclare a package?
512
513       Bareword filehandle "%s" not allowed under 'no feature
514       "bareword_filehandles"'
515           (F) You attempted to use a bareword filehandle with the
516           "bareword_filehandles" feature disabled.
517
518           Only the built-in handles "STDIN", "STDOUT", "STDERR", "ARGV",
519           "ARGVOUT" and "DATA" can be used with the "bareword_filehandles"
520           feature disabled.
521
522       BEGIN failed--compilation aborted
523           (F) An untrapped exception was raised while executing a BEGIN
524           subroutine.  Compilation stops immediately and the interpreter is
525           exited.
526
527       BEGIN not safe after errors--compilation aborted
528           (F) Perl found a "BEGIN {}" subroutine (or a "use" directive, which
529           implies a "BEGIN {}") after one or more compilation errors had
530           already occurred.  Since the intended environment for the "BEGIN
531           {}" could not be guaranteed (due to the errors), and since
532           subsequent code likely depends on its correct operation, Perl just
533           gave up.
534
535       \%d better written as $%d
536           (W syntax) Outside of patterns, backreferences live on as
537           variables.  The use of backslashes is grandfathered on the right-
538           hand side of a substitution, but stylistically it's better to use
539           the variable form because other Perl programmers will expect it,
540           and it works better if there are more than 9 backreferences.
541
542       Binary number > 0b11111111111111111111111111111111 non-portable
543           (W portable) The binary number you specified is larger than 2**32-1
544           (4294967295) and therefore non-portable between systems.  See
545           perlport for more on portability concerns.
546
547       bind() on closed socket %s
548           (W closed) You tried to do a bind on a closed socket.  Did you
549           forget to check the return value of your socket() call?  See "bind"
550           in perlfunc.
551
552       binmode() on closed filehandle %s
553           (W unopened) You tried binmode() on a filehandle that was never
554           opened.  Check your control flow and number of arguments.
555
556       Bit vector size > 32 non-portable
557           (W portable) Using bit vector sizes larger than 32 is non-portable.
558
559       Bizarre copy of %s
560           (P) Perl detected an attempt to copy an internal value that is not
561           copiable.
562
563       Bizarre SvTYPE [%d]
564           (P) When starting a new thread or returning values from a thread,
565           Perl encountered an invalid data type.
566
567       Both or neither range ends should be Unicode in regex; marked by
568       <-- HERE in m/%s/
569           (W regexp) (only under "use re 'strict'" or within "(?[...])")
570
571           In a bracketed character class in a regular expression pattern, you
572           had a range which has exactly one end of it specified using "\N{}",
573           and the other end is specified using a non-portable mechanism.
574           Perl treats the range as a Unicode range, that is, all the
575           characters in it are considered to be the Unicode characters, and
576           which may be different code points on some platforms Perl runs on.
577           For example, "[\N{U+06}-\x08]" is treated as if you had instead
578           said "[\N{U+06}-\N{U+08}]", that is it matches the characters whose
579           code points in Unicode are 6, 7, and 8.  But that "\x08" might
580           indicate that you meant something different, so the warning gets
581           raised.
582
583       Buffer overflow in prime_env_iter: %s
584           (W internal) A warning peculiar to VMS.  While Perl was preparing
585           to iterate over %ENV, it encountered a logical name or symbol
586           definition which was too long, so it was truncated to the string
587           shown.
588
589       Callback called exit
590           (F) A subroutine invoked from an external package via call_sv()
591           exited by calling exit.
592
593       %s() called too early to check prototype
594           (W prototype) You've called a function that has a prototype before
595           the parser saw a definition or declaration for it, and Perl could
596           not check that the call conforms to the prototype.  You need to
597           either add an early prototype declaration for the subroutine in
598           question, or move the subroutine definition ahead of the call to
599           get proper prototype checking.  Alternatively, if you are certain
600           that you're calling the function correctly, you may put an
601           ampersand before the name to avoid the warning.  See perlsub.
602
603       Cannot chr %f
604           (F) You passed an invalid number (like an infinity or not-a-number)
605           to "chr".
606
607       Cannot complete in-place edit of %s: %s
608           (F) Your perl script appears to have changed directory while
609           performing an in-place edit of a file specified by a relative path,
610           and your system doesn't include the directory relative POSIX
611           functions needed to handle that.
612
613       Cannot compress %f in pack
614           (F) You tried compressing an infinity or not-a-number as an
615           unsigned integer with BER, which makes no sense.
616
617       Cannot compress integer in pack
618           (F) An argument to pack("w",...) was too large to compress.  The
619           BER compressed integer format can only be used with positive
620           integers, and you attempted to compress a very large number (>
621           1e308).  See "pack" in perlfunc.
622
623       Cannot compress negative numbers in pack
624           (F) An argument to pack("w",...) was negative.  The BER compressed
625           integer format can only be used with positive integers.  See "pack"
626           in perlfunc.
627
628       Cannot convert a reference to %s to typeglob
629           (F) You manipulated Perl's symbol table directly, stored a
630           reference in it, then tried to access that symbol via conventional
631           Perl syntax.  The access triggers Perl to autovivify that typeglob,
632           but it there is no legal conversion from that type of reference to
633           a typeglob.
634
635       Cannot copy to %s
636           (P) Perl detected an attempt to copy a value to an internal type
637           that cannot be directly assigned to.
638
639       Cannot find encoding "%s"
640           (S io) You tried to apply an encoding that did not exist to a
641           filehandle, either with open() or binmode().
642
643       Cannot open %s as a dirhandle: it is already open as a filehandle
644           (F) You tried to use opendir() to associate a dirhandle to a symbol
645           (glob or scalar) that already holds a filehandle.  Since this idiom
646           might render your code confusing, it was deprecated in Perl 5.10.
647           As of Perl 5.28, it is a fatal error.
648
649       Cannot open %s as a filehandle: it is already open as a dirhandle
650           (F) You tried to use open() to associate a filehandle to a symbol
651           (glob or scalar) that already holds a dirhandle.  Since this idiom
652           might render your code confusing, it was deprecated in Perl 5.10.
653           As of Perl 5.28, it is a fatal error.
654
655       Cannot pack %f with '%c'
656           (F) You tried converting an infinity or not-a-number to an integer,
657           which makes no sense.
658
659       Cannot printf %f with '%c'
660           (F) You tried printing an infinity or not-a-number as a character
661           (%c), which makes no sense.  Maybe you meant '%s', or just
662           stringifying it?
663
664       Cannot set tied @DB::args
665           (F) "caller" tried to set @DB::args, but found it tied.  Tying
666           @DB::args is not supported.  (Before this error was added, it used
667           to crash.)
668
669       Cannot tie unreifiable array
670           (P) You somehow managed to call "tie" on an array that does not
671           keep a reference count on its arguments and cannot be made to do
672           so.  Such arrays are not even supposed to be accessible to Perl
673           code, but are only used internally.
674
675       Cannot yet reorder sv_vcatpvfn() arguments from va_list
676           (F) Some XS code tried to use "sv_vcatpvfn()" or a related function
677           with a format string that specifies explicit indexes for some of
678           the elements, and using a C-style variable-argument list (a
679           "va_list").  This is not currently supported.  XS authors wanting
680           to do this must instead construct a C array of "SV*" scalars
681           containing the arguments.
682
683       Can only compress unsigned integers in pack
684           (F) An argument to pack("w",...) was not an integer.  The BER
685           compressed integer format can only be used with positive integers,
686           and you attempted to compress something else.  See "pack" in
687           perlfunc.
688
689       Can't bless non-reference value
690           (F) Only hard references may be blessed.  This is how Perl
691           "enforces" encapsulation of objects.  See perlobj.
692
693       Can't "break" in a loop topicalizer
694           (F) You called "break", but you're in a "foreach" block rather than
695           a "given" block.  You probably meant to use "next" or "last".
696
697       Can't "break" outside a given block
698           (F) You called "break", but you're not inside a "given" block.
699
700       Can't call method "%s" on an undefined value
701           (F) You used the syntax of a method call, but the slot filled by
702           the object reference or package name contains an undefined value.
703           Something like this will reproduce the error:
704
705               $BADREF = undef;
706               process $BADREF 1,2,3;
707               $BADREF->process(1,2,3);
708
709       Can't call method "%s" on unblessed reference
710           (F) A method call must know in what package it's supposed to run.
711           It ordinarily finds this out from the object reference you supply,
712           but you didn't supply an object reference in this case.  A
713           reference isn't an object reference until it has been blessed.  See
714           perlobj.
715
716       Can't call method "%s" without a package or object reference
717           (F) You used the syntax of a method call, but the slot filled by
718           the object reference or package name contains an expression that
719           returns a defined value which is neither an object reference nor a
720           package name.  Something like this will reproduce the error:
721
722               $BADREF = 42;
723               process $BADREF 1,2,3;
724               $BADREF->process(1,2,3);
725
726       Can't call mro_isa_changed_in() on anonymous symbol table
727           (P) Perl got confused as to whether a hash was a plain hash or a
728           symbol table hash when trying to update @ISA caches.
729
730       Can't call mro_method_changed_in() on anonymous symbol table
731           (F) An XS module tried to call "mro_method_changed_in" on a hash
732           that was not attached to the symbol table.
733
734       Can't chdir to %s
735           (F) You called "perl -x/foo/bar", but /foo/bar is not a directory
736           that you can chdir to, possibly because it doesn't exist.
737
738       Can't check filesystem of script "%s" for nosuid
739           (P) For some reason you can't check the filesystem of the script
740           for nosuid.
741
742       Can't coerce %s to %s in %s
743           (F) Certain types of SVs, in particular real symbol table entries
744           (typeglobs), can't be forced to stop being what they are.  So you
745           can't say things like:
746
747               *foo += 1;
748
749           You CAN say
750
751               $foo = *foo;
752               $foo += 1;
753
754           but then $foo no longer contains a glob.
755
756       Can't "continue" outside a when block
757           (F) You called "continue", but you're not inside a "when" or
758           "default" block.
759
760       Can't create pipe mailbox
761           (P) An error peculiar to VMS.  The process is suffering from
762           exhausted quotas or other plumbing problems.
763
764       Can't declare %s in "%s"
765           (F) Only scalar, array, and hash variables may be declared as "my",
766           "our" or "state" variables.  They must have ordinary identifiers as
767           names.
768
769       Can't "default" outside a topicalizer
770           (F) You have used a "default" block that is neither inside a
771           "foreach" loop nor a "given" block.  (Note that this error is
772           issued on exit from the "default" block, so you won't get the error
773           if you use an explicit "continue".)
774
775       Can't determine class of operator %s, assuming BASEOP
776           (S) This warning indicates something wrong in the internals of
777           perl.  Perl was trying to find the class (e.g. LISTOP) of a
778           particular OP, and was unable to do so. This is likely to be due to
779           a bug in the perl internals, or due to a bug in XS code which
780           manipulates perl optrees.
781
782       Can't do inplace edit: %s is not a regular file
783           (S inplace) You tried to use the -i switch on a special file, such
784           as a file in /dev, a FIFO or an uneditable directory.  The file was
785           ignored.
786
787       Can't do inplace edit on %s: %s
788           (S inplace) The creation of the new file failed for the indicated
789           reason.
790
791       Can't do inplace edit: %s would not be unique
792           (S inplace) Your filesystem does not support filenames longer than
793           14 characters and Perl was unable to create a unique filename
794           during inplace editing with the -i switch.  The file was ignored.
795
796       Can't do %s("%s") on non-UTF-8 locale; resolved to "%s".
797           (W locale) You are 1) running under ""use locale""; 2) the current
798           locale is not a UTF-8 one; 3) you tried to do the designated case-
799           change operation on the specified Unicode character; and 4) the
800           result of this operation would mix Unicode and locale rules, which
801           likely conflict.  Mixing of different rule types is forbidden, so
802           the operation was not done; instead the result is the indicated
803           value, which is the best available that uses entirely Unicode
804           rules.  That turns out to almost always be the original character,
805           unchanged.
806
807           It is generally a bad idea to mix non-UTF-8 locales and Unicode,
808           and this issue is one of the reasons why.  This warning is raised
809           when Unicode rules would normally cause the result of this
810           operation to contain a character that is in the range specified by
811           the locale, 0..255, and hence is subject to the locale's rules, not
812           Unicode's.
813
814           If you are using locale purely for its characteristics related to
815           things like its numeric and time formatting (and not "LC_CTYPE"),
816           consider using a restricted form of the locale pragma (see "The
817           "use locale" pragma" in perllocale) like
818           ""use locale ':not_characters'"".
819
820           Note that failed case-changing operations done as a result of case-
821           insensitive "/i" regular expression matching will show up in this
822           warning as having the "fc" operation (as that is what the regular
823           expression engine calls behind the scenes.)
824
825       Can't do waitpid with flags
826           (F) This machine doesn't have either waitpid() or wait4(), so only
827           waitpid() without flags is emulated.
828
829       Can't emulate -%s on #! line
830           (F) The #! line specifies a switch that doesn't make sense at this
831           point.  For example, it'd be kind of silly to put a -x on the #!
832           line.
833
834       Can't %s %s-endian %ss on this platform
835           (F) Your platform's byte-order is neither big-endian nor little-
836           endian, or it has a very strange pointer size.  Packing and
837           unpacking big- or little-endian floating point values and pointers
838           may not be possible.  See "pack" in perlfunc.
839
840       Can't exec "%s": %s
841           (W exec) A system(), exec(), or piped open call could not execute
842           the named program for the indicated reason.  Typical reasons
843           include: the permissions were wrong on the file, the file wasn't
844           found in $ENV{PATH}, the executable in question was compiled for
845           another architecture, or the #! line in a script points to an
846           interpreter that can't be run for similar reasons.  (Or maybe your
847           system doesn't support #! at all.)
848
849       Can't exec %s
850           (F) Perl was trying to execute the indicated program for you
851           because that's what the #! line said.  If that's not what you
852           wanted, you may need to mention "perl" on the #! line somewhere.
853
854       Can't execute %s
855           (F) You used the -S switch, but the copies of the script to execute
856           found in the PATH did not have correct permissions.
857
858       Can't find an opnumber for "%s"
859           (F) A string of a form "CORE::word" was given to prototype(), but
860           there is no builtin with the name "word".
861
862       Can't find label %s
863           (F) You said to goto a label that isn't mentioned anywhere that
864           it's possible for us to go to.  See "goto" in perlfunc.
865
866       Can't find %s on PATH
867           (F) You used the -S switch, but the script to execute could not be
868           found in the PATH.
869
870       Can't find %s on PATH, '.' not in PATH
871           (F) You used the -S switch, but the script to execute could not be
872           found in the PATH, or at least not with the correct permissions.
873           The script exists in the current directory, but PATH prohibits
874           running it.
875
876       Can't find string terminator %s anywhere before EOF
877           (F) Perl strings can stretch over multiple lines.  This message
878           means that the closing delimiter was omitted.  Because bracketed
879           quotes count nesting levels, the following is missing its final
880           parenthesis:
881
882               print q(The character '(' starts a side comment.);
883
884           If you're getting this error from a here-document, you may have
885           included unseen whitespace before or after your closing tag or
886           there may not be a linebreak after it.  A good programmer's editor
887           will have a way to help you find these characters (or lack of
888           characters).  See perlop for the full details on here-documents.
889
890       Can't find Unicode property definition "%s"
891       Can't find Unicode property definition "%s" in regex; marked by <--
892       HERE in m/%s/
893           (F) The named property which you specified via "\p" or "\P" is not
894           one known to Perl.  Perhaps you misspelled the name?  See
895           "Properties accessible through \p{} and \P{}" in perluniprops for a
896           complete list of available official properties.  If it is a user-
897           defined property it must have been defined by the time the regular
898           expression is matched.
899
900           If you didn't mean to use a Unicode property, escape the "\p",
901           either by "\\p" (just the "\p") or by "\Q\p" (the rest of the
902           string, or until "\E").
903
904       Can't fork: %s
905           (F) A fatal error occurred while trying to fork while opening a
906           pipeline.
907
908       Can't fork, trying again in 5 seconds
909           (W pipe) A fork in a piped open failed with EAGAIN and will be
910           retried after five seconds.
911
912       Can't get filespec - stale stat buffer?
913           (S) A warning peculiar to VMS.  This arises because of the
914           difference between access checks under VMS and under the Unix model
915           Perl assumes.  Under VMS, access checks are done by filename,
916           rather than by bits in the stat buffer, so that ACLs and other
917           protections can be taken into account.  Unfortunately, Perl assumes
918           that the stat buffer contains all the necessary information, and
919           passes it, instead of the filespec, to the access-checking routine.
920           It will try to retrieve the filespec using the device name and FID
921           present in the stat buffer, but this works only if you haven't made
922           a subsequent call to the CRTL stat() routine, because the device
923           name is overwritten with each call.  If this warning appears, the
924           name lookup failed, and the access-checking routine gave up and
925           returned FALSE, just to be conservative.  (Note: The access-
926           checking routine knows about the Perl "stat" operator and file
927           tests, so you shouldn't ever see this warning in response to a Perl
928           command; it arises only if some internal code takes stat buffers
929           lightly.)
930
931       Can't get pipe mailbox device name
932           (P) An error peculiar to VMS.  After creating a mailbox to act as a
933           pipe, Perl can't retrieve its name for later use.
934
935       Can't get SYSGEN parameter value for MAXBUF
936           (P) An error peculiar to VMS.  Perl asked $GETSYI how big you want
937           your mailbox buffers to be, and didn't get an answer.
938
939       Can't "goto" into a binary or list expression
940           (F) A "goto" statement was executed to jump into the middle of a
941           binary or list expression.  You can't get there from here.  The
942           reason for this restriction is that the interpreter would get
943           confused as to how many arguments there are, resulting in stack
944           corruption or crashes.  This error occurs in cases such as these:
945
946               goto F;
947               print do { F: }; # Can't jump into the arguments to print
948
949               goto G;
950               $x + do { G: $y }; # How is + supposed to get its first operand?
951
952       Can't "goto" into a "given" block
953           (F) A "goto" statement was executed to jump into the middle of a
954           "given" block.  You can't get there from here.  See "goto" in
955           perlfunc.
956
957       Can't "goto" into the middle of a foreach loop
958           (F) A "goto" statement was executed to jump into the middle of a
959           foreach loop.  You can't get there from here.  See "goto" in
960           perlfunc.
961
962       Can't "goto" out of a pseudo block
963           (F) A "goto" statement was executed to jump out of what might look
964           like a block, except that it isn't a proper block.  This usually
965           occurs if you tried to jump out of a sort() block or subroutine,
966           which is a no-no.  See "goto" in perlfunc.
967
968       Can't goto subroutine from an eval-%s
969           (F) The "goto subroutine" call can't be used to jump out of an eval
970           "string" or block.
971
972       Can't goto subroutine from a sort sub (or similar callback)
973           (F) The "goto subroutine" call can't be used to jump out of the
974           comparison sub for a sort(), or from a similar callback (such as
975           the reduce() function in List::Util).
976
977       Can't goto subroutine outside a subroutine
978           (F) The deeply magical "goto subroutine" call can only replace one
979           subroutine call for another.  It can't manufacture one out of whole
980           cloth.  In general you should be calling it out of only an AUTOLOAD
981           routine anyway.  See "goto" in perlfunc.
982
983       Can't ignore signal CHLD, forcing to default
984           (W signal) Perl has detected that it is being run with the SIGCHLD
985           signal (sometimes known as SIGCLD) disabled.  Since disabling this
986           signal will interfere with proper determination of exit status of
987           child processes, Perl has reset the signal to its default value.
988           This situation typically indicates that the parent program under
989           which Perl may be running (e.g. cron) is being very careless.
990
991       Can't kill a non-numeric process ID
992           (F) Process identifiers must be (signed) integers.  It is a fatal
993           error to attempt to kill() an undefined, empty-string or otherwise
994           non-numeric process identifier.
995
996       Can't "last" outside a loop block
997           (F) A "last" statement was executed to break out of the current
998           block, except that there's this itty bitty problem called there
999           isn't a current block.  Note that an "if" or "else" block doesn't
1000           count as a "loopish" block, as doesn't a block given to sort(),
1001           map() or grep().  You can usually double the curlies to get the
1002           same effect though, because the inner curlies will be considered a
1003           block that loops once.  See "last" in perlfunc.
1004
1005       Can't linearize anonymous symbol table
1006           (F) Perl tried to calculate the method resolution order (MRO) of a
1007           package, but failed because the package stash has no name.
1008
1009       Can't load '%s' for module %s
1010           (F) The module you tried to load failed to load a dynamic
1011           extension.  This may either mean that you upgraded your version of
1012           perl to one that is incompatible with your old dynamic extensions
1013           (which is known to happen between major versions of perl), or (more
1014           likely) that your dynamic extension was built against an older
1015           version of the library that is installed on your system.  You may
1016           need to rebuild your old dynamic extensions.
1017
1018       Can't localize lexical variable %s
1019           (F) You used local on a variable name that was previously declared
1020           as a lexical variable using "my" or "state".  This is not allowed.
1021           If you want to localize a package variable of the same name,
1022           qualify it with the package name.
1023
1024       Can't localize through a reference
1025           (F) You said something like "local $$ref", which Perl can't
1026           currently handle, because when it goes to restore the old value of
1027           whatever $ref pointed to after the scope of the local() is
1028           finished, it can't be sure that $ref will still be a reference.
1029
1030       Can't locate %s
1031           (F) You said to "do" (or "require", or "use") a file that couldn't
1032           be found.  Perl looks for the file in all the locations mentioned
1033           in @INC, unless the file name included the full path to the file.
1034           Perhaps you need to set the PERL5LIB or PERL5OPT environment
1035           variable to say where the extra library is, or maybe the script
1036           needs to add the library name to @INC.  Or maybe you just
1037           misspelled the name of the file.  See "require" in perlfunc and
1038           lib.
1039
1040       Can't locate auto/%s.al in @INC
1041           (F) A function (or method) was called in a package which allows
1042           autoload, but there is no function to autoload.  Most probable
1043           causes are a misprint in a function/method name or a failure to
1044           "AutoSplit" the file, say, by doing "make install".
1045
1046       Can't locate loadable object for module %s in @INC
1047           (F) The module you loaded is trying to load an external library,
1048           like for example, foo.so or bar.dll, but the DynaLoader module was
1049           unable to locate this library.  See DynaLoader.
1050
1051       Can't locate object method "%s" via package "%s"
1052           (F) You called a method correctly, and it correctly indicated a
1053           package functioning as a class, but that package doesn't define
1054           that particular method, nor does any of its base classes.  See
1055           perlobj.
1056
1057       Can't locate object method "%s" via package "%s" (perhaps you forgot to
1058       load "%s"?)
1059           (F) You called a method on a class that did not exist, and the
1060           method could not be found in UNIVERSAL.  This often means that a
1061           method requires a package that has not been loaded.
1062
1063       Can't locate package %s for @%s::ISA
1064           (W syntax) The @ISA array contained the name of another package
1065           that doesn't seem to exist.
1066
1067       Can't locate PerlIO%s
1068           (F) You tried to use in open() a PerlIO layer that does not exist,
1069           e.g. open(FH, ">:nosuchlayer", "somefile").
1070
1071       Can't make list assignment to %ENV on this system
1072           (F) List assignment to %ENV is not supported on some systems,
1073           notably VMS.
1074
1075       Can't make loaded symbols global on this platform while loading %s
1076           (S) A module passed the flag 0x01 to DynaLoader::dl_load_file() to
1077           request that symbols from the stated file are made available
1078           globally within the process, but that functionality is not
1079           available on this platform.  Whilst the module likely will still
1080           work, this may prevent the perl interpreter from loading other XS-
1081           based extensions which need to link directly to functions defined
1082           in the C or XS code in the stated file.
1083
1084       Can't modify %s in %s
1085           (F) You aren't allowed to assign to the item indicated, or
1086           otherwise try to change it, such as with an auto-increment.
1087
1088       Can't modify nonexistent substring
1089           (P) The internal routine that does assignment to a substr() was
1090           handed a NULL.
1091
1092       Can't modify non-lvalue subroutine call of &%s
1093       Can't modify non-lvalue subroutine call of &%s in %s
1094           (F) Subroutines meant to be used in lvalue context should be
1095           declared as such.  See "Lvalue subroutines" in perlsub.
1096
1097       Can't modify reference to %s in %s assignment
1098           (F) Only a limited number of constructs can be used as the argument
1099           to a reference constructor on the left-hand side of an assignment,
1100           and what you used was not one of them.  See "Assigning to
1101           References" in perlref.
1102
1103       Can't modify reference to localized parenthesized array in list
1104       assignment
1105           (F) Assigning to "\local(@array)" or "\(local @array)" is not
1106           supported, as it is not clear exactly what it should do.  If you
1107           meant to make @array refer to some other array, use "\@array =
1108           \@other_array".  If you want to make the elements of @array aliases
1109           of the scalars referenced on the right-hand side, use "\(@array) =
1110           @scalar_refs".
1111
1112       Can't modify reference to parenthesized hash in list assignment
1113           (F) Assigning to "\(%hash)" is not supported.  If you meant to make
1114           %hash refer to some other hash, use "\%hash = \%other_hash".  If
1115           you want to make the elements of %hash into aliases of the scalars
1116           referenced on the right-hand side, use a hash slice: "\@hash{@keys}
1117           = @those_scalar_refs".
1118
1119       Can't msgrcv to read-only var
1120           (F) The target of a msgrcv must be modifiable to be used as a
1121           receive buffer.
1122
1123       Can't "next" outside a loop block
1124           (F) A "next" statement was executed to reiterate the current block,
1125           but there isn't a current block.  Note that an "if" or "else" block
1126           doesn't count as a "loopish" block, as doesn't a block given to
1127           sort(), map() or grep().  You can usually double the curlies to get
1128           the same effect though, because the inner curlies will be
1129           considered a block that loops once.  See "next" in perlfunc.
1130
1131       Can't open %s: %s
1132           (S inplace) The implicit opening of a file through use of the "<>"
1133           filehandle, either implicitly under the "-n" or "-p" command-line
1134           switches, or explicitly, failed for the indicated reason.  Usually
1135           this is because you don't have read permission for a file which you
1136           named on the command line.
1137
1138           (F) You tried to call perl with the -e switch, but /dev/null (or
1139           your operating system's equivalent) could not be opened.
1140
1141       Can't open a reference
1142           (W io) You tried to open a scalar reference for reading or writing,
1143           using the 3-arg open() syntax:
1144
1145               open FH, '>', $ref;
1146
1147           but your version of perl is compiled without perlio, and this form
1148           of open is not supported.
1149
1150       Can't open bidirectional pipe
1151           (W pipe) You tried to say "open(CMD, "|cmd|")", which is not
1152           supported.  You can try any of several modules in the Perl library
1153           to do this, such as IPC::Open2.  Alternately, direct the pipe's
1154           output to a file using ">", and then read it in under a different
1155           file handle.
1156
1157       Can't open error file %s as stderr
1158           (F) An error peculiar to VMS.  Perl does its own command line
1159           redirection, and couldn't open the file specified after '2>' or
1160           '2>>' on the command line for writing.
1161
1162       Can't open input file %s as stdin
1163           (F) An error peculiar to VMS.  Perl does its own command line
1164           redirection, and couldn't open the file specified after '<' on the
1165           command line for reading.
1166
1167       Can't open output file %s as stdout
1168           (F) An error peculiar to VMS.  Perl does its own command line
1169           redirection, and couldn't open the file specified after '>' or '>>'
1170           on the command line for writing.
1171
1172       Can't open output pipe (name: %s)
1173           (P) An error peculiar to VMS.  Perl does its own command line
1174           redirection, and couldn't open the pipe into which to send data
1175           destined for stdout.
1176
1177       Can't open perl script "%s": %s
1178           (F) The script you specified can't be opened for the indicated
1179           reason.
1180
1181           If you're debugging a script that uses #!, and normally relies on
1182           the shell's $PATH search, the -S option causes perl to do that
1183           search, so you don't have to type the path or "`which
1184           $scriptname`".
1185
1186       Can't read CRTL environ
1187           (S) A warning peculiar to VMS.  Perl tried to read an element of
1188           %ENV from the CRTL's internal environment array and discovered the
1189           array was missing.  You need to figure out where your CRTL
1190           misplaced its environ or define PERL_ENV_TABLES (see perlvms) so
1191           that environ is not searched.
1192
1193       Can't redeclare "%s" in "%s"
1194           (F) A "my", "our" or "state" declaration was found within another
1195           declaration, such as "my ($x, my($y), $z)" or "our (my $x)".
1196
1197       Can't "redo" outside a loop block
1198           (F) A "redo" statement was executed to restart the current block,
1199           but there isn't a current block.  Note that an "if" or "else" block
1200           doesn't count as a "loopish" block, as doesn't a block given to
1201           sort(), map() or grep().  You can usually double the curlies to get
1202           the same effect though, because the inner curlies will be
1203           considered a block that loops once.  See "redo" in perlfunc.
1204
1205       Can't remove %s: %s, skipping file
1206           (S inplace) You requested an inplace edit without creating a backup
1207           file.  Perl was unable to remove the original file to replace it
1208           with the modified file.  The file was left unmodified.
1209
1210       Can't rename in-place work file '%s' to '%s': %s
1211           (F) When closed implicitly, the temporary file for in-place editing
1212           couldn't be renamed to the original filename.
1213
1214       Can't rename %s to %s: %s, skipping file
1215           (F) The rename done by the -i switch failed for some reason,
1216           probably because you don't have write permission to the directory.
1217
1218       Can't reopen input pipe (name: %s) in binary mode
1219           (P) An error peculiar to VMS.  Perl thought stdin was a pipe, and
1220           tried to reopen it to accept binary data.  Alas, it failed.
1221
1222       Can't represent character for Ox%X on this platform
1223           (F) There is a hard limit to how big a character code point can be
1224           due to the fundamental properties of UTF-8, especially on EBCDIC
1225           platforms.  The given code point exceeds that.  The only work-
1226           around is to not use such a large code point.
1227
1228       Can't reset %ENV on this system
1229           (F) You called "reset('E')" or similar, which tried to reset all
1230           variables in the current package beginning with "E".  In the main
1231           package, that includes %ENV.  Resetting %ENV is not supported on
1232           some systems, notably VMS.
1233
1234       Can't resolve method "%s" overloading "%s" in package "%s"
1235           (F)(P) Error resolving overloading specified by a method name (as
1236           opposed to a subroutine reference): no such method callable via the
1237           package.  If the method name is "???", this is an internal error.
1238
1239       Can't return %s from lvalue subroutine
1240           (F) Perl detected an attempt to return illegal lvalues (such as
1241           temporary or readonly values) from a subroutine used as an lvalue.
1242           This is not allowed.
1243
1244       Can't return outside a subroutine
1245           (F) The return statement was executed in mainline code, that is,
1246           where there was no subroutine call to return out of.  See perlsub.
1247
1248       Can't return %s to lvalue scalar context
1249           (F) You tried to return a complete array or hash from an lvalue
1250           subroutine, but you called the subroutine in a way that made Perl
1251           think you meant to return only one value.  You probably meant to
1252           write parentheses around the call to the subroutine, which tell
1253           Perl that the call should be in list context.
1254
1255       Can't stat script "%s"
1256           (P) For some reason you can't fstat() the script even though you
1257           have it open already.  Bizarre.
1258
1259       Can't take log of %g
1260           (F) For ordinary real numbers, you can't take the logarithm of a
1261           negative number or zero.  There's a Math::Complex package that
1262           comes standard with Perl, though, if you really want to do that for
1263           the negative numbers.
1264
1265       Can't take sqrt of %g
1266           (F) For ordinary real numbers, you can't take the square root of a
1267           negative number.  There's a Math::Complex package that comes
1268           standard with Perl, though, if you really want to do that.
1269
1270       Can't undef active subroutine
1271           (F) You can't undefine a routine that's currently running.  You
1272           can, however, redefine it while it's running, and you can even
1273           undef the redefined subroutine while the old routine is running.
1274           Go figure.
1275
1276       Can't unweaken a nonreference
1277           (F) You attempted to unweaken something that was not a reference.
1278           Only references can be unweakened.
1279
1280       Can't upgrade %s (%d) to %d
1281           (P) The internal sv_upgrade routine adds "members" to an SV, making
1282           it into a more specialized kind of SV.  The top several SV types
1283           are so specialized, however, that they cannot be interconverted.
1284           This message indicates that such a conversion was attempted.
1285
1286       Can't use '%c' after -mname
1287           (F) You tried to call perl with the -m switch, but you put
1288           something other than "=" after the module name.
1289
1290       Can't use a hash as a reference
1291           (F) You tried to use a hash as a reference, as in "%foo->{"bar"}"
1292           or "%$ref->{"hello"}".  Versions of perl <= 5.22.0 used to allow
1293           this syntax, but shouldn't have.  This was deprecated in perl
1294           5.6.1.
1295
1296       Can't use an array as a reference
1297           (F) You tried to use an array as a reference, as in "@foo->[23]" or
1298           "@$ref->[99]".  Versions of perl <= 5.22.0 used to allow this
1299           syntax, but shouldn't have.  This was deprecated in perl 5.6.1.
1300
1301       Can't use anonymous symbol table for method lookup
1302           (F) The internal routine that does method lookup was handed a
1303           symbol table that doesn't have a name.  Symbol tables can become
1304           anonymous for example by undefining stashes: "undef
1305           %Some::Package::".
1306
1307       Can't use an undefined value as %s reference
1308           (F) A value used as either a hard reference or a symbolic reference
1309           must be a defined value.  This helps to delurk some insidious
1310           errors.
1311
1312       Can't use bareword ("%s") as %s ref while "strict refs" in use
1313           (F) Only hard references are allowed by "strict refs".  Symbolic
1314           references are disallowed.  See perlref.
1315
1316       Can't use %! because Errno.pm is not available
1317           (F) The first time the "%!" hash is used, perl automatically loads
1318           the Errno.pm module.  The Errno module is expected to tie the %!
1319           hash to provide symbolic names for $! errno values.
1320
1321       Can't use both '<' and '>' after type '%c' in %s
1322           (F) A type cannot be forced to have both big-endian and little-
1323           endian byte-order at the same time, so this combination of
1324           modifiers is not allowed.  See "pack" in perlfunc.
1325
1326       Can't use 'defined(@array)' (Maybe you should just omit the defined()?)
1327           (F) defined() is not useful on arrays because it checks for an
1328           undefined scalar value.  If you want to see if the array is empty,
1329           just use "if (@array) { # not empty }" for example.
1330
1331       Can't use 'defined(%hash)' (Maybe you should just omit the defined()?)
1332           (F) "defined()" is not usually right on hashes.
1333
1334           Although "defined %hash" is false on a plain not-yet-used hash, it
1335           becomes true in several non-obvious circumstances, including
1336           iterators, weak references, stash names, even remaining true after
1337           "undef %hash".  These things make "defined %hash" fairly useless in
1338           practice, so it now generates a fatal error.
1339
1340           If a check for non-empty is what you wanted then just put it in
1341           boolean context (see "Scalar values" in perldata):
1342
1343               if (%hash) {
1344                  # not empty
1345               }
1346
1347           If you had "defined %Foo::Bar::QUUX" to check whether such a
1348           package variable exists then that's never really been reliable, and
1349           isn't a good way to enquire about the features of a package, or
1350           whether it's loaded, etc.
1351
1352       Can't use %s for loop variable
1353           (P) The parser got confused when trying to parse a "foreach" loop.
1354
1355       Can't use global %s in %s
1356           (F) You tried to declare a magical variable as a lexical variable.
1357           This is not allowed, because the magic can be tied to only one
1358           location (namely the global variable) and it would be incredibly
1359           confusing to have variables in your program that looked like
1360           magical variables but weren't.
1361
1362       Can't use '%c' in a group with different byte-order in %s
1363           (F) You attempted to force a different byte-order on a type that is
1364           already inside a group with a byte-order modifier.  For example you
1365           cannot force little-endianness on a type that is inside a big-
1366           endian group.
1367
1368       Can't use "my %s" in sort comparison
1369           (F) The global variables $a and $b are reserved for sort
1370           comparisons.  You mentioned $a or $b in the same line as the <=> or
1371           cmp operator, and the variable had earlier been declared as a
1372           lexical variable.  Either qualify the sort variable with the
1373           package name, or rename the lexical variable.
1374
1375       Can't use %s ref as %s ref
1376           (F) You've mixed up your reference types.  You have to dereference
1377           a reference of the type needed.  You can use the ref() function to
1378           test the type of the reference, if need be.
1379
1380       Can't use string ("%s") as %s ref while "strict refs" in use
1381       Can't use string ("%s"...) as %s ref while "strict refs" in use
1382           (F) You've told Perl to dereference a string, something which "use
1383           strict" blocks to prevent it happening accidentally.  See "Symbolic
1384           references" in perlref.  This can be triggered by an "@" or "$" in
1385           a double-quoted string immediately before interpolating a variable,
1386           for example in "user @$twitter_id", which says to treat the
1387           contents of $twitter_id as an array reference; use a "\" to have a
1388           literal "@" symbol followed by the contents of $twitter_id: "user
1389           \@$twitter_id".
1390
1391       Can't use subscript on %s
1392           (F) The compiler tried to interpret a bracketed expression as a
1393           subscript.  But to the left of the brackets was an expression that
1394           didn't look like a hash or array reference, or anything else
1395           subscriptable.
1396
1397       Can't use \%c to mean $%c in expression
1398           (W syntax) In an ordinary expression, backslash is a unary operator
1399           that creates a reference to its argument.  The use of backslash to
1400           indicate a backreference to a matched substring is valid only as
1401           part of a regular expression pattern.  Trying to do this in
1402           ordinary Perl code produces a value that prints out looking like
1403           SCALAR(0xdecaf).  Use the $1 form instead.
1404
1405       Can't weaken a nonreference
1406           (F) You attempted to weaken something that was not a reference.
1407           Only references can be weakened.
1408
1409       Can't "when" outside a topicalizer
1410           (F) You have used a when() block that is neither inside a "foreach"
1411           loop nor a "given" block.  (Note that this error is issued on exit
1412           from the "when" block, so you won't get the error if the match
1413           fails, or if you use an explicit "continue".)
1414
1415       Can't x= to read-only value
1416           (F) You tried to repeat a constant value (often the undefined
1417           value) with an assignment operator, which implies modifying the
1418           value itself.  Perhaps you need to copy the value to a temporary,
1419           and repeat that.
1420
1421       Character following "\c" must be printable ASCII
1422           (F) In "\cX", X must be a printable (non-control) ASCII character.
1423
1424           Note that ASCII characters that don't map to control characters are
1425           discouraged, and will generate the warning (when enabled) ""\c%c"
1426           is more clearly written simply as "%s"".
1427
1428       Character following \%c must be '{' or a single-character Unicode
1429       property name in regex; marked by <-- HERE in m/%s/
1430           (F) (In the above the %c is replaced by either "p" or "P".)  You
1431           specified something that isn't a legal Unicode property name.  Most
1432           Unicode properties are specified by "\p{...}".  But if the name is
1433           a single character one, the braces may be omitted.
1434
1435       Character in 'C' format wrapped in pack
1436           (W pack) You said
1437
1438               pack("C", $x)
1439
1440           where $x is either less than 0 or more than 255; the "C" format is
1441           only for encoding native operating system characters (ASCII,
1442           EBCDIC, and so on) and not for Unicode characters, so Perl behaved
1443           as if you meant
1444
1445               pack("C", $x & 255)
1446
1447           If you actually want to pack Unicode codepoints, use the "U" format
1448           instead.
1449
1450       Character in 'c' format wrapped in pack
1451           (W pack) You said
1452
1453               pack("c", $x)
1454
1455           where $x is either less than -128 or more than 127; the "c" format
1456           is only for encoding native operating system characters (ASCII,
1457           EBCDIC, and so on) and not for Unicode characters, so Perl behaved
1458           as if you meant
1459
1460               pack("c", $x & 255);
1461
1462           If you actually want to pack Unicode codepoints, use the "U" format
1463           instead.
1464
1465       Character in '%c' format wrapped in unpack
1466           (W unpack) You tried something like
1467
1468              unpack("H", "\x{2a1}")
1469
1470           where the format expects to process a byte (a character with a
1471           value below 256), but a higher value was provided instead.  Perl
1472           uses the value modulus 256 instead, as if you had provided:
1473
1474              unpack("H", "\x{a1}")
1475
1476       Character in 'W' format wrapped in pack
1477           (W pack) You said
1478
1479               pack("U0W", $x)
1480
1481           where $x is either less than 0 or more than 255.  However,
1482           "U0"-mode expects all values to fall in the interval [0, 255], so
1483           Perl behaved as if you meant:
1484
1485               pack("U0W", $x & 255)
1486
1487       Character(s) in '%c' format wrapped in pack
1488           (W pack) You tried something like
1489
1490              pack("u", "\x{1f3}b")
1491
1492           where the format expects to process a sequence of bytes (character
1493           with a value below 256), but some of the characters had a higher
1494           value.  Perl uses the character values modulus 256 instead, as if
1495           you had provided:
1496
1497              pack("u", "\x{f3}b")
1498
1499       Character(s) in '%c' format wrapped in unpack
1500           (W unpack) You tried something like
1501
1502              unpack("s", "\x{1f3}b")
1503
1504           where the format expects to process a sequence of bytes (character
1505           with a value below 256), but some of the characters had a higher
1506           value.  Perl uses the character values modulus 256 instead, as if
1507           you had provided:
1508
1509              unpack("s", "\x{f3}b")
1510
1511       charnames alias definitions may not contain a sequence of multiple
1512       spaces; marked by <-- HERE in %s
1513           (F) You defined a character name which had multiple space
1514           characters in a row.  Change them to single spaces.  Usually these
1515           names are defined in the ":alias" import argument to "use
1516           charnames", but they could be defined by a translator installed
1517           into $^H{charnames}.  See "CUSTOM ALIASES" in charnames.
1518
1519       chdir() on unopened filehandle %s
1520           (W unopened) You tried chdir() on a filehandle that was never
1521           opened.
1522
1523       "\c%c" is more clearly written simply as "%s"
1524           (W syntax) The "\cX" construct is intended to be a way to specify
1525           non-printable characters.  You used it for a printable one, which
1526           is better written as simply itself, perhaps preceded by a backslash
1527           for non-word characters.  Doing it the way you did is not portable
1528           between ASCII and EBCDIC platforms.
1529
1530       Cloning substitution context is unimplemented
1531           (F) Creating a new thread inside the "s///" operator is not
1532           supported.
1533
1534       closedir() attempted on invalid dirhandle %s
1535           (W io) The dirhandle you tried to close is either closed or not
1536           really a dirhandle.  Check your control flow.
1537
1538       close() on unopened filehandle %s
1539           (W unopened) You tried to close a filehandle that was never opened.
1540
1541       Closure prototype called
1542           (F) If a closure has attributes, the subroutine passed to an
1543           attribute handler is the prototype that is cloned when a new
1544           closure is created.  This subroutine cannot be called.
1545
1546       \C no longer supported in regex; marked by <-- HERE in m/%s/
1547           (F) The \C character class used to allow a match of single byte
1548           within a multi-byte utf-8 character, but was removed in v5.24 as it
1549           broke encapsulation and its implementation was extremely buggy.  If
1550           you really need to process the individual bytes, you probably want
1551           to convert your string to one where each underlying byte is stored
1552           as a character, with utf8::encode().
1553
1554       Code missing after '/'
1555           (F) You had a (sub-)template that ends with a '/'.  There must be
1556           another template code following the slash.  See "pack" in perlfunc.
1557
1558       Code point 0x%X is not Unicode, and not portable
1559           (S non_unicode portable) You had a code point that has never been
1560           in any standard, so it is likely that languages other than Perl
1561           will NOT understand it.  This code point also will not fit in a
1562           32-bit word on ASCII platforms and therefore is non-portable
1563           between systems.
1564
1565           At one time, it was legal in some standards to have code points up
1566           to 0x7FFF_FFFF, but not higher, and this code point is higher.
1567
1568           Acceptance of these code points is a Perl extension, and you should
1569           expect that nothing other than Perl can handle them; Perl itself on
1570           EBCDIC platforms before v5.24 does not handle them.
1571
1572           Perl also makes no guarantees that the representation of these code
1573           points won't change at some point in the future, say when machines
1574           become available that have larger than a 64-bit word.  At that
1575           time, files containing any of these, written by an older Perl might
1576           require conversion before being readable by a newer Perl.
1577
1578       Code point 0x%X is not Unicode, may not be portable
1579           (S non_unicode) You had a code point above the Unicode maximum of
1580           U+10FFFF.
1581
1582           Perl allows strings to contain a superset of Unicode code points,
1583           but these may not be accepted by other languages/systems.  Further,
1584           even if these languages/systems accept these large code points,
1585           they may have chosen a different representation for them than the
1586           UTF-8-like one that Perl has, which would mean files are not
1587           exchangeable between them and Perl.
1588
1589           On EBCDIC platforms, code points above 0x3FFF_FFFF have a different
1590           representation in Perl v5.24 than before, so any file containing
1591           these that was written before that version will require conversion
1592           before being readable by a later Perl.
1593
1594       %s: Command not found
1595           (A) You've accidentally run your script through csh or another
1596           shell instead of Perl.  Check the #! line, or manually feed your
1597           script into Perl yourself.  The #! line at the top of your file
1598           could look like
1599
1600             #!/usr/bin/perl
1601
1602       %s: command not found
1603           (A) You've accidentally run your script through bash or another
1604           shell instead of Perl.  Check the #! line, or manually feed your
1605           script into Perl yourself.  The #! line at the top of your file
1606           could look like
1607
1608             #!/usr/bin/perl
1609
1610       %s: command not found: %s
1611           (A) You've accidentally run your script through zsh or another
1612           shell instead of Perl.  Check the #! line, or manually feed your
1613           script into Perl yourself.  The #! line at the top of your file
1614           could look like
1615
1616             #!/usr/bin/perl
1617
1618       Compilation failed in require
1619           (F) Perl could not compile a file specified in a "require"
1620           statement.  Perl uses this generic message when none of the errors
1621           that it encountered were severe enough to halt compilation
1622           immediately.
1623
1624       Complex regular subexpression recursion limit (%d) exceeded
1625           (W regexp) The regular expression engine uses recursion in complex
1626           situations where back-tracking is required.  Recursion depth is
1627           limited to 32766, or perhaps less in architectures where the stack
1628           cannot grow arbitrarily.  ("Simple" and "medium" situations are
1629           handled without recursion and are not subject to a limit.)  Try
1630           shortening the string under examination; looping in Perl code (e.g.
1631           with "while") rather than in the regular expression engine; or
1632           rewriting the regular expression so that it is simpler or
1633           backtracks less.  (See perlfaq2 for information on Mastering
1634           Regular Expressions.)
1635
1636       connect() on closed socket %s
1637           (W closed) You tried to do a connect on a closed socket.  Did you
1638           forget to check the return value of your socket() call?  See
1639           "connect" in perlfunc.
1640
1641       Constant(%s): Call to &{$^H{%s}} did not return a defined value
1642           (F) The subroutine registered to handle constant overloading (see
1643           overload) or a custom charnames handler (see "CUSTOM TRANSLATORS"
1644           in charnames) returned an undefined value.
1645
1646       Constant(%s): $^H{%s} is not defined
1647           (F) The parser found inconsistencies while attempting to define an
1648           overloaded constant.  Perhaps you forgot to load the corresponding
1649           overload pragma?
1650
1651       Constant is not %s reference
1652           (F) A constant value (perhaps declared using the "use constant"
1653           pragma) is being dereferenced, but it amounts to the wrong type of
1654           reference.  The message indicates the type of reference that was
1655           expected.  This usually indicates a syntax error in dereferencing
1656           the constant value.  See "Constant Functions" in perlsub and
1657           constant.
1658
1659       Constants from lexical variables potentially modified elsewhere are no
1660       longer permitted
1661           (F) You wrote something like
1662
1663               my $var;
1664               $sub = sub () { $var };
1665
1666           but $var is referenced elsewhere and could be modified after the
1667           "sub" expression is evaluated.  Either it is explicitly modified
1668           elsewhere ("$var = 3") or it is passed to a subroutine or to an
1669           operator like "printf" or "map", which may or may not modify the
1670           variable.
1671
1672           Traditionally, Perl has captured the value of the variable at that
1673           point and turned the subroutine into a constant eligible for
1674           inlining.  In those cases where the variable can be modified
1675           elsewhere, this breaks the behavior of closures, in which the
1676           subroutine captures the variable itself, rather than its value, so
1677           future changes to the variable are reflected in the subroutine's
1678           return value.
1679
1680           This usage was deprecated, and as of Perl 5.32 is no longer
1681           allowed, making it possible to change the behavior in the future.
1682
1683           If you intended for the subroutine to be eligible for inlining,
1684           then make sure the variable is not referenced elsewhere, possibly
1685           by copying it:
1686
1687               my $var2 = $var;
1688               $sub = sub () { $var2 };
1689
1690           If you do want this subroutine to be a closure that reflects future
1691           changes to the variable that it closes over, add an explicit
1692           "return":
1693
1694               my $var;
1695               $sub = sub () { return $var };
1696
1697       Constant subroutine %s redefined
1698           (W redefine)(S) You redefined a subroutine which had previously
1699           been eligible for inlining.  See "Constant Functions" in perlsub
1700           for commentary and workarounds.
1701
1702       Constant subroutine %s undefined
1703           (W misc) You undefined a subroutine which had previously been
1704           eligible for inlining.  See "Constant Functions" in perlsub for
1705           commentary and workarounds.
1706
1707       Constant(%s) unknown
1708           (F) The parser found inconsistencies either while attempting to
1709           define an overloaded constant, or when trying to find the character
1710           name specified in the "\N{...}" escape.  Perhaps you forgot to load
1711           the corresponding overload pragma?
1712
1713       :const is experimental
1714           (S experimental::const_attr) The "const" attribute is experimental.
1715           If you want to use the feature, disable the warning with "no
1716           warnings 'experimental::const_attr'", but know that in doing so you
1717           are taking the risk that your code may break in a future Perl
1718           version.
1719
1720       :const is not permitted on named subroutines
1721           (F) The "const" attribute causes an anonymous subroutine to be run
1722           and its value captured at the time that it is cloned.  Named
1723           subroutines are not cloned like this, so the attribute does not
1724           make sense on them.
1725
1726       Copy method did not return a reference
1727           (F) The method which overloads "=" is buggy.  See "Copy
1728           Constructor" in overload.
1729
1730       &CORE::%s cannot be called directly
1731           (F) You tried to call a subroutine in the "CORE::" namespace with
1732           &foo syntax or through a reference.  Some subroutines in this
1733           package cannot yet be called that way, but must be called as
1734           barewords.  Something like this will work:
1735
1736               BEGIN { *shove = \&CORE::push; }
1737               shove @array, 1,2,3; # pushes on to @array
1738
1739       CORE::%s is not a keyword
1740           (F) The CORE:: namespace is reserved for Perl keywords.
1741
1742       Corrupted regexp opcode %d > %d
1743           (P) This is either an error in Perl, or, if you're using one, your
1744           custom regular expression engine.  If not the latter, report the
1745           problem to <https://github.com/Perl/perl5/issues>.
1746
1747       corrupted regexp pointers
1748           (P) The regular expression engine got confused by what the regular
1749           expression compiler gave it.
1750
1751       corrupted regexp program
1752           (P) The regular expression engine got passed a regexp program
1753           without a valid magic number.
1754
1755       Corrupt malloc ptr 0x%x at 0x%x
1756           (P) The malloc package that comes with Perl had an internal
1757           failure.
1758
1759       Count after length/code in unpack
1760           (F) You had an unpack template indicating a counted-length string,
1761           but you have also specified an explicit size for the string.  See
1762           "pack" in perlfunc.
1763
1764       Declaring references is experimental
1765           (S experimental::declared_refs) This warning is emitted if you use
1766           a reference constructor on the right-hand side of "my", "state",
1767           "our", or "local".  Simply suppress the warning if you want to use
1768           the feature, but know that in doing so you are taking the risk of
1769           using an experimental feature which may change or be removed in a
1770           future Perl version:
1771
1772               no warnings "experimental::declared_refs";
1773               use feature "declared_refs";
1774               $fooref = my \$foo;
1775
1776       Deep recursion on anonymous subroutine
1777       Deep recursion on subroutine "%s"
1778           (W recursion) This subroutine has called itself (directly or
1779           indirectly) 100 times more than it has returned.  This probably
1780           indicates an infinite recursion, unless you're writing strange
1781           benchmark programs, in which case it indicates something else.
1782
1783           This threshold can be changed from 100, by recompiling the perl
1784           binary, setting the C pre-processor macro "PERL_SUB_DEPTH_WARN" to
1785           the desired value.
1786
1787       (?(DEFINE)....) does not allow branches in regex; marked by <-- HERE in
1788       m/%s/
1789           (F) You used something like "(?(DEFINE)...|..)" which is illegal.
1790           The most likely cause of this error is that you left out a
1791           parenthesis inside of the "...." part.
1792
1793           The <-- HERE shows whereabouts in the regular expression the
1794           problem was discovered.
1795
1796       %s defines neither package nor VERSION--version check failed
1797           (F) You said something like "use Module 42" but in the Module file
1798           there are neither package declarations nor a $VERSION.
1799
1800       delete argument is not a HASH or ARRAY element or slice
1801           (F) The argument to "delete" must be either a hash or array
1802           element, such as:
1803
1804               $foo{$bar}
1805               $ref->{"susie"}[12]
1806
1807           or a hash or array slice, such as:
1808
1809               @foo[$bar, $baz, $xyzzy]
1810               $ref->[12]->@{"susie", "queue"}
1811
1812           or a hash key/value or array index/value slice, such as:
1813
1814               %foo[$bar, $baz, $xyzzy]
1815               $ref->[12]->%{"susie", "queue"}
1816
1817       Delimiter for here document is too long
1818           (F) In a here document construct like "<<FOO", the label "FOO" is
1819           too long for Perl to handle.  You have to be seriously twisted to
1820           write code that triggers this error.
1821
1822       Deprecated use of my() in false conditional. This will be a fatal error
1823       in Perl 5.30
1824           (D deprecated) You used a declaration similar to "my $x if 0".
1825           There has been a long-standing bug in Perl that causes a lexical
1826           variable not to be cleared at scope exit when its declaration
1827           includes a false conditional.  Some people have exploited this bug
1828           to achieve a kind of static variable.  Since we intend to fix this
1829           bug, we don't want people relying on this behavior.  You can
1830           achieve a similar static effect by declaring the variable in a
1831           separate block outside the function, eg
1832
1833               sub f { my $x if 0; return $x++ }
1834
1835           becomes
1836
1837               { my $x; sub f { return $x++ } }
1838
1839           Beginning with perl 5.10.0, you can also use "state" variables to
1840           have lexicals that are initialized only once (see feature):
1841
1842               sub f { state $x; return $x++ }
1843
1844           This use of "my()" in a false conditional has been deprecated since
1845           Perl 5.10, and it will become a fatal error in Perl 5.30.
1846
1847       DESTROY created new reference to dead object '%s'
1848           (F) A DESTROY() method created a new reference to the object which
1849           is just being DESTROYed.  Perl is confused, and prefers to abort
1850           rather than to create a dangling reference.
1851
1852       Did not produce a valid header
1853           See "500 Server error".
1854
1855       %s did not return a true value
1856           (F) A required (or used) file must return a true value to indicate
1857           that it compiled correctly and ran its initialization code
1858           correctly.  It's traditional to end such a file with a "1;", though
1859           any true value would do.  See "require" in perlfunc.
1860
1861       (Did you mean &%s instead?)
1862           (W misc) You probably referred to an imported subroutine &FOO as
1863           $FOO or some such.
1864
1865       (Did you mean "local" instead of "our"?)
1866           (W shadow) Remember that "our" does not localize the declared
1867           global variable.  You have declared it again in the same lexical
1868           scope, which seems superfluous.
1869
1870       (Did you mean $ or @ instead of %?)
1871           (W) You probably said %hash{$key} when you meant $hash{$key} or
1872           @hash{@keys}.  On the other hand, maybe you just meant %hash and
1873           got carried away.
1874
1875       Died
1876           (F) You passed die() an empty string (the equivalent of "die """)
1877           or you called it with no args and $@ was empty.
1878
1879       Document contains no data
1880           See "500 Server error".
1881
1882       %s does not define %s::VERSION--version check failed
1883           (F) You said something like "use Module 42" but the Module did not
1884           define a $VERSION.
1885
1886       '/' does not take a repeat count
1887           (F) You cannot put a repeat count of any kind right after the '/'
1888           code.  See "pack" in perlfunc.
1889
1890       do "%s" failed, '.' is no longer in @INC; did you mean do "./%s"?
1891           (D deprecated) Previously " do "somefile"; " would search the
1892           current directory for the specified file.  Since perl v5.26.0, .
1893           has been removed from @INC by default, so this is no longer true.
1894           To search the current directory (and only the current directory)
1895           you can write " do "./somefile"; ".
1896
1897       Don't know how to get file name
1898           (P) "PerlIO_getname", a perl internal I/O function specific to VMS,
1899           was somehow called on another platform.  This should not happen.
1900
1901       Don't know how to handle magic of type \%o
1902           (P) The internal handling of magical variables has been cursed.
1903
1904       do_study: out of memory
1905           (P) This should have been caught by safemalloc() instead.
1906
1907       (Do you need to predeclare %s?)
1908           (S syntax) This is an educated guess made in conjunction with the
1909           message "%s found where operator expected".  It often means a
1910           subroutine or module name is being referenced that hasn't been
1911           declared yet.  This may be because of ordering problems in your
1912           file, or because of a missing "sub", "package", "require", or "use"
1913           statement.  If you're referencing something that isn't defined yet,
1914           you don't actually have to define the subroutine or package before
1915           the current location.  You can use an empty "sub foo;" or "package
1916           FOO;" to enter a "forward" declaration.
1917
1918       dump() must be written as CORE::dump() as of Perl 5.30
1919           (F) You used the obsolete "dump()" built-in function.  That was
1920           deprecated in Perl 5.8.0.  As of Perl 5.30 it must be written in
1921           fully qualified format: "CORE::dump()".
1922
1923           See "dump" in perlfunc.
1924
1925       dump is not supported
1926           (F) Your machine doesn't support dump/undump.
1927
1928       Duplicate free() ignored
1929           (S malloc) An internal routine called free() on something that had
1930           already been freed.
1931
1932       Duplicate modifier '%c' after '%c' in %s
1933           (W unpack) You have applied the same modifier more than once after
1934           a type in a pack template.  See "pack" in perlfunc.
1935
1936       elseif should be elsif
1937           (S syntax) There is no keyword "elseif" in Perl because Larry
1938           thinks it's ugly.  Your code will be interpreted as an attempt to
1939           call a method named "elseif" for the class returned by the
1940           following block.  This is unlikely to be what you want.
1941
1942       Empty \%c in regex; marked by <-- HERE in m/%s/
1943       Empty \%c{}
1944       Empty \%c{} in regex; marked by <-- HERE in m/%s/
1945           (F) You used something like "\b{}", "\B{}", "\o{}", "\p", "\P", or
1946           "\x" without specifying anything for it to operate on.
1947
1948           Unfortunately, for backwards compatibility reasons, an empty "\x"
1949           is legal outside "use re 'strict'" and expands to a NUL character.
1950
1951       Empty (?) without any modifiers in regex; marked by <-- HERE in m/%s/
1952           (W regexp) (only under "use re 'strict'") "(?)" does nothing, so
1953           perhaps this is a typo.
1954
1955       ${^ENCODING} is no longer supported
1956           (F) The special variable "${^ENCODING}", formerly used to implement
1957           the "encoding" pragma, is no longer supported as of Perl 5.26.0.
1958
1959           Setting it to anything other than "undef" is a fatal error as of
1960           Perl 5.28.
1961
1962       entering effective %s failed
1963           (F) While under the "use filetest" pragma, switching the real and
1964           effective uids or gids failed.
1965
1966       %ENV is aliased to %s
1967           (F) You're running under taint mode, and the %ENV variable has been
1968           aliased to another hash, so it doesn't reflect anymore the state of
1969           the program's environment.  This is potentially insecure.
1970
1971       Error converting file specification %s
1972           (F) An error peculiar to VMS.  Because Perl may have to deal with
1973           file specifications in either VMS or Unix syntax, it converts them
1974           to a single form when it must operate on them directly.  Either
1975           you've passed an invalid file specification to Perl, or you've
1976           found a case the conversion routines don't handle.  Drat.
1977
1978       Error %s in expansion of %s
1979           (F) An error was encountered in handling a user-defined property
1980           ("User-Defined Character Properties" in perlunicode).  These are
1981           programmer written subroutines, hence subject to errors that may
1982           prevent them from compiling or running.  The calls to these subs
1983           are "eval"'d, and if there is a failure, this message is raised,
1984           using the contents of $@ from the failed "eval".
1985
1986           Another possibility is that tainted data was encountered somewhere
1987           in the chain of expanding the property.  If so, the message wording
1988           will indicate that this is the problem.  See "Insecure user-defined
1989           property %s".
1990
1991       Eval-group in insecure regular expression
1992           (F) Perl detected tainted data when trying to compile a regular
1993           expression that contains the "(?{ ... })" zero-width assertion,
1994           which is unsafe.  See "(?{ code })" in perlre, and perlsec.
1995
1996       Eval-group not allowed at runtime, use re 'eval' in regex m/%s/
1997           (F) Perl tried to compile a regular expression containing the "(?{
1998           ... })" zero-width assertion at run time, as it would when the
1999           pattern contains interpolated values.  Since that is a security
2000           risk, it is not allowed.  If you insist, you may still do this by
2001           using the "re 'eval'" pragma or by explicitly building the pattern
2002           from an interpolated string at run time and using that in an
2003           eval().  See "(?{ code })" in perlre.
2004
2005       Eval-group not allowed, use re 'eval' in regex m/%s/
2006           (F) A regular expression contained the "(?{ ... })" zero-width
2007           assertion, but that construct is only allowed when the "use re
2008           'eval'" pragma is in effect.  See "(?{ code })" in perlre.
2009
2010       EVAL without pos change exceeded limit in regex; marked by <-- HERE in
2011       m/%s/
2012           (F) You used a pattern that nested too many EVAL calls without
2013           consuming any text.  Restructure the pattern so that text is
2014           consumed.
2015
2016           The <-- HERE shows whereabouts in the regular expression the
2017           problem was discovered.
2018
2019       Excessively long <> operator
2020           (F) The contents of a <> operator may not exceed the maximum size
2021           of a Perl identifier.  If you're just trying to glob a long list of
2022           filenames, try using the glob() operator, or put the filenames into
2023           a variable and glob that.
2024
2025       exec? I'm not *that* kind of operating system
2026           (F) The "exec" function is not implemented on some systems, e.g.
2027           Catamount. See perlport.
2028
2029       %sExecution of %s aborted due to compilation errors.
2030           (F) The final summary message when a Perl compilation fails.
2031
2032       exists argument is not a HASH or ARRAY element or a subroutine
2033           (F) The argument to "exists" must be a hash or array element or a
2034           subroutine with an ampersand, such as:
2035
2036               $foo{$bar}
2037               $ref->{"susie"}[12]
2038               &do_something
2039
2040       exists argument is not a subroutine name
2041           (F) The argument to "exists" for "exists &sub" must be a subroutine
2042           name, and not a subroutine call.  "exists &sub()" will generate
2043           this error.
2044
2045       Exiting eval via %s
2046           (W exiting) You are exiting an eval by unconventional means, such
2047           as a goto, or a loop control statement.
2048
2049       Exiting format via %s
2050           (W exiting) You are exiting a format by unconventional means, such
2051           as a goto, or a loop control statement.
2052
2053       Exiting pseudo-block via %s
2054           (W exiting) You are exiting a rather special block construct (like
2055           a sort block or subroutine) by unconventional means, such as a
2056           goto, or a loop control statement.  See "sort" in perlfunc.
2057
2058       Exiting subroutine via %s
2059           (W exiting) You are exiting a subroutine by unconventional means,
2060           such as a goto, or a loop control statement.
2061
2062       Exiting substitution via %s
2063           (W exiting) You are exiting a substitution by unconventional means,
2064           such as a return, a goto, or a loop control statement.
2065
2066       Expecting close bracket in regex; marked by <-- HERE in m/%s/
2067           (F) You wrote something like
2068
2069            (?13
2070
2071           to denote a capturing group of the form "(?PARNO)", but omitted the
2072           ")".
2073
2074       Expecting interpolated extended charclass in regex; marked by <-- HERE
2075       in m/%s/
2076           (F) It looked like you were attempting to interpolate an already-
2077           compiled extended character class, like so:
2078
2079            my $thai_or_lao = qr/(?[ \p{Thai} + \p{Lao} ])/;
2080            ...
2081            qr/(?[ \p{Digit} & $thai_or_lao ])/;
2082
2083           But the marked code isn't syntactically correct to be such an
2084           interpolated class.
2085
2086       Experimental aliasing via reference not enabled
2087           (F) To do aliasing via references, you must first enable the
2088           feature:
2089
2090               no warnings "experimental::refaliasing";
2091               use feature "refaliasing";
2092               \$x = \$y;
2093
2094       Experimental %s on scalar is now forbidden
2095           (F) An experimental feature added in Perl 5.14 allowed "each",
2096           "keys", "push", "pop", "shift", "splice", "unshift", and "values"
2097           to be called with a scalar argument.  This experiment is considered
2098           unsuccessful, and has been removed.  The "postderef" feature may
2099           meet your needs better.
2100
2101       Experimental subroutine signatures not enabled
2102           (F) To use subroutine signatures, you must first enable them:
2103
2104               no warnings "experimental::signatures";
2105               use feature "signatures";
2106               sub foo ($left, $right) { ... }
2107
2108       Explicit blessing to '' (assuming package main)
2109           (W misc) You are blessing a reference to a zero length string.
2110           This has the effect of blessing the reference into the package
2111           main.  This is usually not what you want.  Consider providing a
2112           default target package, e.g. bless($ref, $p || 'MyPackage');
2113
2114       %s: Expression syntax
2115           (A) You've accidentally run your script through csh instead of
2116           Perl.  Check the #! line, or manually feed your script into Perl
2117           yourself.
2118
2119       %s failed--call queue aborted
2120           (F) An untrapped exception was raised while executing a UNITCHECK,
2121           CHECK, INIT, or END subroutine.  Processing of the remainder of the
2122           queue of such routines has been prematurely ended.
2123
2124       Failed to close in-place work file %s: %s
2125           (F) Closing an output file from in-place editing, as with the "-i"
2126           command-line switch, failed.
2127
2128       False [] range "%s" in regex; marked by <-- HERE in m/%s/
2129           (W regexp)(F) A character class range must start and end at a
2130           literal character, not another character class like "\d" or
2131           "[:alpha:]".  The "-" in your false range is interpreted as a
2132           literal "-".  In a "(?[...])"  construct, this is an error, rather
2133           than a warning.  Consider quoting the "-", "\-".  The <-- HERE
2134           shows whereabouts in the regular expression the problem was
2135           discovered.  See perlre.
2136
2137       Fatal VMS error (status=%d) at %s, line %d
2138           (P) An error peculiar to VMS.  Something untoward happened in a VMS
2139           system service or RTL routine; Perl's exit status should provide
2140           more details.  The filename in "at %s" and the line number in "line
2141           %d" tell you which section of the Perl source code is distressed.
2142
2143       fcntl is not implemented
2144           (F) Your machine apparently doesn't implement fcntl().  What is
2145           this, a PDP-11 or something?
2146
2147       FETCHSIZE returned a negative value
2148           (F) A tied array claimed to have a negative number of elements,
2149           which is not possible.
2150
2151       Field too wide in 'u' format in pack
2152           (W pack) Each line in an uuencoded string starts with a length
2153           indicator which can't encode values above 63.  So there is no point
2154           in asking for a line length bigger than that.  Perl will behave as
2155           if you specified "u63" as the format.
2156
2157       File::Glob::glob() will disappear in perl 5.30. Use
2158       File::Glob::bsd_glob() instead.
2159           (D deprecated) "File::Glob" has a function called "glob", which
2160           just calls "bsd_glob". However, its prototype is different from the
2161           prototype of "CORE::glob", and hence, "File::Glob::glob" should not
2162           be used.
2163
2164           "File::Glob::glob()" was deprecated in perl 5.8.0. A deprecation
2165           message was issued from perl 5.26.0 onwards, and the function will
2166           disappear in perl 5.30.0.
2167
2168           Code using "File::Glob::glob()" should call
2169           "File::Glob::bsd_glob()" instead.
2170
2171       Filehandle %s opened only for input
2172           (W io) You tried to write on a read-only filehandle.  If you
2173           intended it to be a read-write filehandle, you needed to open it
2174           with "+<" or "+>" or "+>>" instead of with "<" or nothing.  If you
2175           intended only to write the file, use ">" or ">>".  See "open" in
2176           perlfunc.
2177
2178       Filehandle %s opened only for output
2179           (W io) You tried to read from a filehandle opened only for writing,
2180           If you intended it to be a read/write filehandle, you needed to
2181           open it with "+<" or "+>" or "+>>" instead of with ">".  If you
2182           intended only to read from the file, use "<".  See "open" in
2183           perlfunc.  Another possibility is that you attempted to open
2184           filedescriptor 0 (also known as STDIN) for output (maybe you closed
2185           STDIN earlier?).
2186
2187       Filehandle %s reopened as %s only for input
2188           (W io) You opened for reading a filehandle that got the same
2189           filehandle id as STDOUT or STDERR.  This occurred because you
2190           closed STDOUT or STDERR previously.
2191
2192       Filehandle STDIN reopened as %s only for output
2193           (W io) You opened for writing a filehandle that got the same
2194           filehandle id as STDIN.  This occurred because you closed STDIN
2195           previously.
2196
2197       Final $ should be \$ or $name
2198           (F) You must now decide whether the final $ in a string was meant
2199           to be a literal dollar sign, or was meant to introduce a variable
2200           name that happens to be missing.  So you have to put either the
2201           backslash or the name.
2202
2203       flock() on closed filehandle %s
2204           (W closed) The filehandle you're attempting to flock() got itself
2205           closed some time before now.  Check your control flow.  flock()
2206           operates on filehandles.  Are you attempting to call flock() on a
2207           dirhandle by the same name?
2208
2209       Format not terminated
2210           (F) A format must be terminated by a line with a solitary dot.
2211           Perl got to the end of your file without finding such a line.
2212
2213       Format %s redefined
2214           (W redefine) You redefined a format.  To suppress this warning, say
2215
2216               {
2217                   no warnings 'redefine';
2218                   eval "format NAME =...";
2219               }
2220
2221       Found = in conditional, should be ==
2222           (W syntax) You said
2223
2224               if ($foo = 123)
2225
2226           when you meant
2227
2228               if ($foo == 123)
2229
2230           (or something like that).
2231
2232       %s found where operator expected
2233           (S syntax) The Perl lexer knows whether to expect a term or an
2234           operator.  If it sees what it knows to be a term when it was
2235           expecting to see an operator, it gives you this warning.  Usually
2236           it indicates that an operator or delimiter was omitted, such as a
2237           semicolon.
2238
2239       gdbm store returned %d, errno %d, key "%s"
2240           (S) A warning from the GDBM_File extension that a store failed.
2241
2242       gethostent not implemented
2243           (F) Your C library apparently doesn't implement gethostent(),
2244           probably because if it did, it'd feel morally obligated to return
2245           every hostname on the Internet.
2246
2247       get%sname() on closed socket %s
2248           (W closed) You tried to get a socket or peer socket name on a
2249           closed socket.  Did you forget to check the return value of your
2250           socket() call?
2251
2252       getpwnam returned invalid UIC %#o for user "%s"
2253           (S) A warning peculiar to VMS.  The call to "sys$getuai" underlying
2254           the "getpwnam" operator returned an invalid UIC.
2255
2256       getsockopt() on closed socket %s
2257           (W closed) You tried to get a socket option on a closed socket.
2258           Did you forget to check the return value of your socket() call?
2259           See "getsockopt" in perlfunc.
2260
2261       given is experimental
2262           (S experimental::smartmatch) "given" depends on smartmatch, which
2263           is experimental, so its behavior may change or even be removed in
2264           any future release of perl.  See the explanation under
2265           "Experimental Details on given and when" in perlsyn.
2266
2267       Global symbol "%s" requires explicit package name (did you forget to
2268       declare "my %s"?)
2269           (F) You've said "use strict" or "use strict vars", which indicates
2270           that all variables must either be lexically scoped (using "my" or
2271           "state"), declared beforehand using "our", or explicitly qualified
2272           to say which package the global variable is in (using "::").
2273
2274       glob failed (%s)
2275           (S glob) Something went wrong with the external program(s) used for
2276           "glob" and "<*.c>".  Usually, this means that you supplied a "glob"
2277           pattern that caused the external program to fail and exit with a
2278           nonzero status.  If the message indicates that the abnormal exit
2279           resulted in a coredump, this may also mean that your csh (C shell)
2280           is broken.  If so, you should change all of the csh-related
2281           variables in config.sh:  If you have tcsh, make the variables refer
2282           to it as if it were csh (e.g. "full_csh='/usr/bin/tcsh'");
2283           otherwise, make them all empty (except that "d_csh" should be
2284           'undef') so that Perl will think csh is missing.  In either case,
2285           after editing config.sh, run "./Configure -S" and rebuild Perl.
2286
2287       Glob not terminated
2288           (F) The lexer saw a left angle bracket in a place where it was
2289           expecting a term, so it's looking for the corresponding right angle
2290           bracket, and not finding it.  Chances are you left some needed
2291           parentheses out earlier in the line, and you really meant a "less
2292           than".
2293
2294       gmtime(%f) failed
2295           (W overflow) You called "gmtime" with a number that it could not
2296           handle: too large, too small, or NaN.  The returned value is
2297           "undef".
2298
2299       gmtime(%f) too large
2300           (W overflow) You called "gmtime" with a number that was larger than
2301           it can reliably handle and "gmtime" probably returned the wrong
2302           date.  This warning is also triggered with NaN (the special not-a-
2303           number value).
2304
2305       gmtime(%f) too small
2306           (W overflow) You called "gmtime" with a number that was smaller
2307           than it can reliably handle and "gmtime" probably returned the
2308           wrong date.
2309
2310       Got an error from DosAllocMem
2311           (P) An error peculiar to OS/2.  Most probably you're using an
2312           obsolete version of Perl, and this should not happen anyway.
2313
2314       goto must have label
2315           (F) Unlike with "next" or "last", you're not allowed to goto an
2316           unspecified destination.  See "goto" in perlfunc.
2317
2318       Goto undefined subroutine%s
2319           (F) You tried to call a subroutine with "goto &sub" syntax, but the
2320           indicated subroutine hasn't been defined, or if it was, it has
2321           since been undefined.
2322
2323       Group name must start with a non-digit word character in regex; marked
2324       by <-- HERE in m/%s/
2325           (F) Group names must follow the rules for perl identifiers, meaning
2326           they must start with a non-digit word character.  A common cause of
2327           this error is using (?&0) instead of (?0).  See perlre.
2328
2329       ()-group starts with a count
2330           (F) A ()-group started with a count.  A count is supposed to follow
2331           something: a template character or a ()-group.  See "pack" in
2332           perlfunc.
2333
2334       %s had compilation errors.
2335           (F) The final summary message when a "perl -c" fails.
2336
2337       Had to create %s unexpectedly
2338           (S internal) A routine asked for a symbol from a symbol table that
2339           ought to have existed already, but for some reason it didn't, and
2340           had to be created on an emergency basis to prevent a core dump.
2341
2342       %s has too many errors
2343           (F) The parser has given up trying to parse the program after 10
2344           errors.  Further error messages would likely be uninformative.
2345
2346       Hexadecimal float: exponent overflow
2347           (W overflow) The hexadecimal floating point has a larger exponent
2348           than the floating point supports.
2349
2350       Hexadecimal float: exponent underflow
2351           (W overflow) The hexadecimal floating point has a smaller exponent
2352           than the floating point supports.  With the IEEE 754 floating
2353           point, this may also mean that the subnormals (formerly known as
2354           denormals) are being used, which may or may not be an error.
2355
2356       Hexadecimal float: internal error (%s)
2357           (F) Something went horribly bad in hexadecimal float handling.
2358
2359       Hexadecimal float: mantissa overflow
2360           (W overflow) The hexadecimal floating point literal had more bits
2361           in the mantissa (the part between the 0x and the exponent, also
2362           known as the fraction or the significand) than the floating point
2363           supports.
2364
2365       Hexadecimal float: precision loss
2366           (W overflow) The hexadecimal floating point had internally more
2367           digits than could be output.  This can be caused by unsupported
2368           long double formats, or by 64-bit integers not being available
2369           (needed to retrieve the digits under some configurations).
2370
2371       Hexadecimal float: unsupported long double format
2372           (F) You have configured Perl to use long doubles but the internals
2373           of the long double format are unknown; therefore the hexadecimal
2374           float output is impossible.
2375
2376       Hexadecimal number > 0xffffffff non-portable
2377           (W portable) The hexadecimal number you specified is larger than
2378           2**32-1 (4294967295) and therefore non-portable between systems.
2379           See perlport for more on portability concerns.
2380
2381       Identifier too long
2382           (F) Perl limits identifiers (names for variables, functions, etc.)
2383           to about 250 characters for simple names, and somewhat more for
2384           compound names (like $A::B).  You've exceeded Perl's limits.
2385           Future versions of Perl are likely to eliminate these arbitrary
2386           limitations.
2387
2388       Ignoring zero length \N{} in character class in regex; marked by
2389       <-- HERE in m/%s/
2390           (W regexp) Named Unicode character escapes ("\N{...}") may return a
2391           zero-length sequence.  When such an escape is used in a character
2392           class its behavior is not well defined.  Check that the correct
2393           escape has been used, and the correct charname handler is in scope.
2394
2395       Illegal %s digit '%c' ignored
2396           (W digit) Here %s is one of "binary", "octal", or "hex".  You may
2397           have tried to use a digit other than one that is legal for the
2398           given type, such as only 0 and 1 for binary.  For octals, this is
2399           raised only if the illegal character is an '8' or '9'.  For hex,
2400           'A' - 'F' and 'a' - 'f' are legal.  Interpretation of the number
2401           stopped just before the offending digit or character.
2402
2403       Illegal binary digit '%c'
2404           (F) You used a digit other than 0 or 1 in a binary number.
2405
2406       Illegal character after '_' in prototype for %s : %s
2407           (W illegalproto) An illegal character was found in a prototype
2408           declaration.  The '_' in a prototype must be followed by a ';',
2409           indicating the rest of the parameters are optional, or one of '@'
2410           or '%', since those two will accept 0 or more final parameters.
2411
2412       Illegal character \%o (carriage return)
2413           (F) Perl normally treats carriage returns in the program text as it
2414           would any other whitespace, which means you should never see this
2415           error when Perl was built using standard options.  For some reason,
2416           your version of Perl appears to have been built without this
2417           support.  Talk to your Perl administrator.
2418
2419       Illegal character following sigil in a subroutine signature
2420           (F) A parameter in a subroutine signature contained an unexpected
2421           character following the "$", "@" or "%" sigil character.  Normally
2422           the sigil should be followed by the variable name or "=" etc.
2423           Perhaps you are trying use a prototype while in the scope of "use
2424           feature 'signatures'"?  For example:
2425
2426               sub foo ($$) {}            # legal - a prototype
2427
2428               use feature 'signatures;
2429               sub foo ($$) {}            # illegal - was expecting a signature
2430               sub foo ($a, $b)
2431                       :prototype($$) {}  # legal
2432
2433       Illegal character in prototype for %s : %s
2434           (W illegalproto) An illegal character was found in a prototype
2435           declaration.  Legal characters in prototypes are $, @, %, *, ;, [,
2436           ], &, \, and +.  Perhaps you were trying to write a subroutine
2437           signature but didn't enable that feature first ("use feature
2438           'signatures'"), so your signature was instead interpreted as a bad
2439           prototype.
2440
2441       Illegal declaration of anonymous subroutine
2442           (F) When using the "sub" keyword to construct an anonymous
2443           subroutine, you must always specify a block of code.  See perlsub.
2444
2445       Illegal declaration of subroutine %s
2446           (F) A subroutine was not declared correctly.  See perlsub.
2447
2448       Illegal division by zero
2449           (F) You tried to divide a number by 0.  Either something was wrong
2450           in your logic, or you need to put a conditional in to guard against
2451           meaningless input.
2452
2453       Illegal modulus zero
2454           (F) You tried to divide a number by 0 to get the remainder.  Most
2455           numbers don't take to this kindly.
2456
2457       Illegal number of bits in vec
2458           (F) The number of bits in vec() (the third argument) must be a
2459           power of two from 1 to 32 (or 64, if your platform supports that).
2460
2461       Illegal octal digit '%c'
2462           (F) You used an 8 or 9 in an octal number.
2463
2464       Illegal operator following parameter in a subroutine signature
2465           (F) A parameter in a subroutine signature, was followed by
2466           something other than "=" introducing a default, "," or ")".
2467
2468               use feature 'signatures';
2469               sub foo ($=1) {}           # legal
2470               sub foo ($a = 1) {}        # legal
2471               sub foo ($a += 1) {}       # illegal
2472               sub foo ($a == 1) {}       # illegal
2473
2474       Illegal pattern in regex; marked by <-- HERE in m/%s/
2475           (F) You wrote something like
2476
2477            (?+foo)
2478
2479           The "+" is valid only when followed by digits, indicating a
2480           capturing group.  See "(?PARNO)".
2481
2482       Illegal suidscript
2483           (F) The script run under suidperl was somehow illegal.
2484
2485       Illegal switch in PERL5OPT: -%c
2486           (X) The PERL5OPT environment variable may only be used to set the
2487           following switches: -[CDIMUdmtw].
2488
2489       Illegal user-defined property name
2490           (F) You specified a Unicode-like property name in a regular
2491           expression pattern (using "\p{}" or "\P{}") that Perl knows isn't
2492           an official Unicode property, and was likely meant to be a user-
2493           defined property name, but it can't be one of those, as they must
2494           begin with either "In" or "Is".  Check the spelling.  See also
2495           "Can't find Unicode property definition "%s"".
2496
2497       Ill-formed CRTL environ value "%s"
2498           (W internal) A warning peculiar to VMS.  Perl tried to read the
2499           CRTL's internal environ array, and encountered an element without
2500           the "=" delimiter used to separate keys from values.  The element
2501           is ignored.
2502
2503       Ill-formed message in prime_env_iter: |%s|
2504           (W internal) A warning peculiar to VMS.  Perl tried to read a
2505           logical name or CLI symbol definition when preparing to iterate
2506           over %ENV, and didn't see the expected delimiter between key and
2507           value, so the line was ignored.
2508
2509       (in cleanup) %s
2510           (W misc) This prefix usually indicates that a DESTROY() method
2511           raised the indicated exception.  Since destructors are usually
2512           called by the system at arbitrary points during execution, and
2513           often a vast number of times, the warning is issued only once for
2514           any number of failures that would otherwise result in the same
2515           message being repeated.
2516
2517           Failure of user callbacks dispatched using the "G_KEEPERR" flag
2518           could also result in this warning.  See "G_KEEPERR" in perlcall.
2519
2520       Incomplete expression within '(?[ ])' in regex; marked by <-- HERE in
2521       m/%s/
2522           (F) There was a syntax error within the "(?[ ])".  This can happen
2523           if the expression inside the construct was completely empty, or if
2524           there are too many or few operands for the number of operators.
2525           Perl is not smart enough to give you a more precise indication as
2526           to what is wrong.
2527
2528       Inconsistent hierarchy during C3 merge of class '%s': merging failed on
2529       parent '%s'
2530           (F) The method resolution order (MRO) of the given class is not
2531           C3-consistent, and you have enabled the C3 MRO for this class.  See
2532           the C3 documentation in mro for more information.
2533
2534       Indentation on line %d of here-doc doesn't match delimiter
2535           (F) You have an indented here-document where one or more of its
2536           lines have whitespace at the beginning that does not match the
2537           closing delimiter.
2538
2539           For example, line 2 below is wrong because it does not have at
2540           least 2 spaces, but lines 1 and 3 are fine because they have at
2541           least 2:
2542
2543               if ($something) {
2544                 print <<~EOF;
2545                   Line 1
2546                  Line 2 not
2547                     Line 3
2548                   EOF
2549               }
2550
2551           Note that tabs and spaces are compared strictly, meaning 1 tab will
2552           not match 8 spaces.
2553
2554       Infinite recursion in regex
2555           (F) You used a pattern that references itself without consuming any
2556           input text.  You should check the pattern to ensure that recursive
2557           patterns either consume text or fail.
2558
2559       Infinite recursion in user-defined property
2560           (F) A user-defined property ("User-Defined Character Properties" in
2561           perlunicode) can depend on the definitions of other user-defined
2562           properties.  If the chain of dependencies leads back to this
2563           property, infinite recursion would occur, were it not for the check
2564           that raised this error.
2565
2566           Restructure your property definitions to avoid this.
2567
2568       Infinite recursion via empty pattern
2569           (F) You tried to use the empty pattern inside of a regex code
2570           block, for instance "/(?{ s!!! })/", which resulted in re-executing
2571           the same pattern, which is an infinite loop which is broken by
2572           throwing an exception.
2573
2574       Initialization of state variables in list currently forbidden
2575           (F) "state" only permits initializing a single variable, specified
2576           without parentheses.  So "state $a = 42" and "state @a = qw(a b c)"
2577           are allowed, but not "state ($a) = 42" or "(state $a) = 42".  To
2578           initialize more than one "state" variable, initialize them one at a
2579           time.
2580
2581       %%s[%s] in scalar context better written as $%s[%s]
2582           (W syntax) In scalar context, you've used an array index/value
2583           slice (indicated by %) to select a single element of an array.
2584           Generally it's better to ask for a scalar value (indicated by $).
2585           The difference is that $foo[&bar] always behaves like a scalar,
2586           both in the value it returns and when evaluating its argument,
2587           while %foo[&bar] provides a list context to its subscript, which
2588           can do weird things if you're expecting only one subscript.  When
2589           called in list context, it also returns the index (what &bar
2590           returns) in addition to the value.
2591
2592       %%s{%s} in scalar context better written as $%s{%s}
2593           (W syntax) In scalar context, you've used a hash key/value slice
2594           (indicated by %) to select a single element of a hash.  Generally
2595           it's better to ask for a scalar value (indicated by $).  The
2596           difference is that $foo{&bar} always behaves like a scalar, both in
2597           the value it returns and when evaluating its argument, while
2598           @foo{&bar} and provides a list context to its subscript, which can
2599           do weird things if you're expecting only one subscript.  When
2600           called in list context, it also returns the key in addition to the
2601           value.
2602
2603       Insecure dependency in %s
2604           (F) You tried to do something that the tainting mechanism didn't
2605           like.  The tainting mechanism is turned on when you're running
2606           setuid or setgid, or when you specify -T to turn it on explicitly.
2607           The tainting mechanism labels all data that's derived directly or
2608           indirectly from the user, who is considered to be unworthy of your
2609           trust.  If any such data is used in a "dangerous" operation, you
2610           get this error.  See perlsec for more information.
2611
2612       Insecure directory in %s
2613           (F) You can't use system(), exec(), or a piped open in a setuid or
2614           setgid script if $ENV{PATH} contains a directory that is writable
2615           by the world.  Also, the PATH must not contain any relative
2616           directory.  See perlsec.
2617
2618       Insecure $ENV{%s} while running %s
2619           (F) You can't use system(), exec(), or a piped open in a setuid or
2620           setgid script if any of $ENV{PATH}, $ENV{IFS}, $ENV{CDPATH},
2621           $ENV{ENV}, $ENV{BASH_ENV} or $ENV{TERM} are derived from data
2622           supplied (or potentially supplied) by the user.  The script must
2623           set the path to a known value, using trustworthy data.  See
2624           perlsec.
2625
2626       Insecure user-defined property %s
2627           (F) Perl detected tainted data when trying to compile a regular
2628           expression that contains a call to a user-defined character
2629           property function, i.e. "\p{IsFoo}" or "\p{InFoo}".  See "User-
2630           Defined Character Properties" in perlunicode and perlsec.
2631
2632       Integer overflow in format string for %s
2633           (F) The indexes and widths specified in the format string of
2634           "printf()" or "sprintf()" are too large.  The numbers must not
2635           overflow the size of integers for your architecture.
2636
2637       Integer overflow in %s number
2638           (S overflow) The hexadecimal, octal or binary number you have
2639           specified either as a literal or as an argument to hex() or oct()
2640           is too big for your architecture, and has been converted to a
2641           floating point number.  On a 32-bit architecture the largest
2642           hexadecimal, octal or binary number representable without overflow
2643           is 0xFFFFFFFF, 037777777777, or 0b11111111111111111111111111111111
2644           respectively.  Note that Perl transparently promotes all numbers to
2645           a floating point representation internally--subject to loss of
2646           precision errors in subsequent operations.
2647
2648       Integer overflow in srand
2649           (S overflow) The number you have passed to srand is too big to fit
2650           in your architecture's integer representation.  The number has been
2651           replaced with the largest integer supported (0xFFFFFFFF on 32-bit
2652           architectures).  This means you may be getting less randomness than
2653           you expect, because different random seeds above the maximum will
2654           return the same sequence of random numbers.
2655
2656       Integer overflow in version
2657       Integer overflow in version %d
2658           (W overflow) Some portion of a version initialization is too large
2659           for the size of integers for your architecture.  This is not a
2660           warning because there is no rational reason for a version to try
2661           and use an element larger than typically 2**32.  This is usually
2662           caused by trying to use some odd mathematical operation as a
2663           version, like 100/9.
2664
2665       Internal disaster in regex; marked by <-- HERE in m/%s/
2666           (P) Something went badly wrong in the regular expression parser.
2667           The <-- HERE shows whereabouts in the regular expression the
2668           problem was discovered.
2669
2670       Internal inconsistency in tracking vforks
2671           (S) A warning peculiar to VMS.  Perl keeps track of the number of
2672           times you've called "fork" and "exec", to determine whether the
2673           current call to "exec" should affect the current script or a
2674           subprocess (see "exec LIST" in perlvms).  Somehow, this count has
2675           become scrambled, so Perl is making a guess and treating this
2676           "exec" as a request to terminate the Perl script and execute the
2677           specified command.
2678
2679       internal %<num>p might conflict with future printf extensions
2680           (S internal) Perl's internal routine that handles "printf" and
2681           "sprintf" formatting follows a slightly different set of rules when
2682           called from C or XS code.  Specifically, formats consisting of
2683           digits followed by "p" (e.g., "%7p") are reserved for future use.
2684           If you see this message, then an XS module tried to call that
2685           routine with one such reserved format.
2686
2687       Internal urp in regex; marked by <-- HERE in m/%s/
2688           (P) Something went badly awry in the regular expression parser.
2689           The <-- HERE shows whereabouts in the regular expression the
2690           problem was discovered.
2691
2692       %s (...) interpreted as function
2693           (W syntax) You've run afoul of the rule that says that any list
2694           operator followed by parentheses turns into a function, with all
2695           the list operators arguments found inside the parentheses.  See
2696           "Terms and List Operators (Leftward)" in perlop.
2697
2698       In '(?...)', the '(' and '?' must be adjacent in regex; marked by
2699       <-- HERE in m/%s/
2700           (F) The two-character sequence "(?" in this context in a regular
2701           expression pattern should be an indivisible token, with nothing
2702           intervening between the "(" and the "?", but you separated them
2703           with whitespace.
2704
2705       In '(*...)', the '(' and '*' must be adjacent in regex; marked by
2706       <-- HERE in m/%s/
2707           (F) The two-character sequence "(*" in this context in a regular
2708           expression pattern should be an indivisible token, with nothing
2709           intervening between the "(" and the "*", but you separated them.
2710           Fix the pattern and retry.
2711
2712       Invalid %s attribute: %s
2713           (F) The indicated attribute for a subroutine or variable was not
2714           recognized by Perl or by a user-supplied handler.  See attributes.
2715
2716       Invalid %s attributes: %s
2717           (F) The indicated attributes for a subroutine or variable were not
2718           recognized by Perl or by a user-supplied handler.  See attributes.
2719
2720       Invalid character in charnames alias definition; marked by <-- HERE in
2721       '%s
2722           (F) You tried to create a custom alias for a character name, with
2723           the ":alias" option to "use charnames" and the specified character
2724           in the indicated name isn't valid.  See "CUSTOM ALIASES" in
2725           charnames.
2726
2727       Invalid \0 character in %s for %s: %s\0%s
2728           (W syscalls) Embedded \0 characters in pathnames or other system
2729           call arguments produce a warning as of 5.20.  The parts after the
2730           \0 were formerly ignored by system calls.
2731
2732       Invalid character in \N{...}; marked by <-- HERE in \N{%s}
2733           (F) Only certain characters are valid for character names.  The
2734           indicated one isn't.  See "CUSTOM ALIASES" in charnames.
2735
2736       Invalid conversion in %s: "%s"
2737           (W printf) Perl does not understand the given format conversion.
2738           See "sprintf" in perlfunc.
2739
2740       Invalid escape in the specified encoding in regex; marked by <-- HERE
2741       in m/%s/
2742           (W regexp)(F) The numeric escape (for example "\xHH") of value <
2743           256 didn't correspond to a single character through the conversion
2744           from the encoding specified by the encoding pragma.  The escape was
2745           replaced with REPLACEMENT CHARACTER (U+FFFD) instead, except within
2746           "(?[   ])", where it is a fatal error.  The <-- HERE shows
2747           whereabouts in the regular expression the escape was discovered.
2748
2749       Invalid hexadecimal number in \N{U+...}
2750       Invalid hexadecimal number in \N{U+...} in regex; marked by <-- HERE in
2751       m/%s/
2752           (F) The character constant represented by "..." is not a valid
2753           hexadecimal number.  Either it is empty, or you tried to use a
2754           character other than 0 - 9 or A - F, a - f in a hexadecimal number.
2755
2756       Invalid module name %s with -%c option: contains single ':'
2757           (F) The module argument to perl's -m and -M command-line options
2758           cannot contain single colons in the module name, but only in the
2759           arguments after "=".  In other words, -MFoo::Bar=:baz is ok, but
2760           -MFoo:Bar=baz is not.
2761
2762       Invalid mro name: '%s'
2763           (F) You tried to "mro::set_mro("classname", "foo")" or "use mro
2764           'foo'", where "foo" is not a valid method resolution order (MRO).
2765           Currently, the only valid ones supported are "dfs" and "c3", unless
2766           you have loaded a module that is a MRO plugin.  See mro and
2767           perlmroapi.
2768
2769       Invalid negative number (%s) in chr
2770           (W utf8) You passed a negative number to "chr".  Negative numbers
2771           are not valid character numbers, so it returns the Unicode
2772           replacement character (U+FFFD).
2773
2774       Invalid number '%s' for -C option.
2775           (F) You supplied a number to the -C option that either has extra
2776           leading zeroes or overflows perl's unsigned integer representation.
2777
2778       invalid option -D%c, use -D'' to see choices
2779           (S debugging) Perl was called with invalid debugger flags.  Call
2780           perl with the -D option with no flags to see the list of acceptable
2781           values.  See also "-Dletters" in perlrun.
2782
2783       Invalid quantifier in {,} in regex; marked by <-- HERE in m/%s/
2784           (F) The pattern looks like a {min,max} quantifier, but the min or
2785           max could not be parsed as a valid number - either it has leading
2786           zeroes, or it represents too big a number to cope with.  The
2787           <-- HERE shows where in the regular expression the problem was
2788           discovered.  See perlre.
2789
2790       Invalid [] range "%s" in regex; marked by <-- HERE in m/%s/
2791           (F) The range specified in a character class had a minimum
2792           character greater than the maximum character.  One possibility is
2793           that you forgot the "{}" from your ending "\x{}" - "\x" without the
2794           curly braces can go only up to "ff".  The <-- HERE shows
2795           whereabouts in the regular expression the problem was discovered.
2796           See perlre.
2797
2798       Invalid range "%s" in transliteration operator
2799           (F) The range specified in the tr/// or y/// operator had a minimum
2800           character greater than the maximum character.  See perlop.
2801
2802       Invalid reference to group in regex; marked by <-- HERE in m/%s/
2803           (F) The capture group you specified can't possibly exist because
2804           the number you used is not within the legal range of possible
2805           values for this machine.
2806
2807       Invalid separator character %s in attribute list
2808           (F) Something other than a colon or whitespace was seen between the
2809           elements of an attribute list.  If the previous attribute had a
2810           parenthesised parameter list, perhaps that list was terminated too
2811           soon.  See attributes.
2812
2813       Invalid separator character %s in PerlIO layer specification %s
2814           (W layer) When pushing layers onto the Perl I/O system, something
2815           other than a colon or whitespace was seen between the elements of a
2816           layer list.  If the previous attribute had a parenthesised
2817           parameter list, perhaps that list was terminated too soon.
2818
2819       Invalid strict version format (%s)
2820           (F) A version number did not meet the "strict" criteria for
2821           versions.  A "strict" version number is a positive decimal number
2822           (integer or decimal-fraction) without exponentiation or else a
2823           dotted-decimal v-string with a leading 'v' character and at least
2824           three components.  The parenthesized text indicates which criteria
2825           were not met.  See the version module for more details on allowed
2826           version formats.
2827
2828       Invalid type '%s' in %s
2829           (F) The given character is not a valid pack or unpack type.  See
2830           "pack" in perlfunc.
2831
2832           (W) The given character is not a valid pack or unpack type but used
2833           to be silently ignored.
2834
2835       Invalid version format (%s)
2836           (F) A version number did not meet the "lax" criteria for versions.
2837           A "lax" version number is a positive decimal number (integer or
2838           decimal-fraction) without exponentiation or else a dotted-decimal
2839           v-string.  If the v-string has fewer than three components, it must
2840           have a leading 'v' character.  Otherwise, the leading 'v' is
2841           optional.  Both decimal and dotted-decimal versions may have a
2842           trailing "alpha" component separated by an underscore character
2843           after a fractional or dotted-decimal component.  The parenthesized
2844           text indicates which criteria were not met.  See the version module
2845           for more details on allowed version formats.
2846
2847       Invalid version object
2848           (F) The internal structure of the version object was invalid.
2849           Perhaps the internals were modified directly in some way or an
2850           arbitrary reference was blessed into the "version" class.
2851
2852       In '(*VERB...)', the '(' and '*' must be adjacent in regex; marked by
2853       <-- HERE in m/%s/
2854       Inverting a character class which contains a multi-character sequence
2855       is illegal in regex; marked by <-- HERE in m/%s/
2856           (F) You wrote something like
2857
2858            qr/\P{name=KATAKANA LETTER AINU P}/
2859            qr/[^\p{name=KATAKANA LETTER AINU P}]/
2860
2861           This name actually evaluates to a sequence of two Katakana
2862           characters, not just a single one, and it is illegal to try to take
2863           the complement of a sequence.  (Mathematically it would mean any
2864           sequence of characters from 0 to infinity in length that weren't
2865           these two in a row, and that is likely not of any real use.)
2866
2867           (F) The two-character sequence "(*" in this context in a regular
2868           expression pattern should be an indivisible token, with nothing
2869           intervening between the "(" and the "*", but you separated them.
2870
2871       ioctl is not implemented
2872           (F) Your machine apparently doesn't implement ioctl(), which is
2873           pretty strange for a machine that supports C.
2874
2875       ioctl() on unopened %s
2876           (W unopened) You tried ioctl() on a filehandle that was never
2877           opened.  Check your control flow and number of arguments.
2878
2879       IO layers (like '%s') unavailable
2880           (F) Your Perl has not been configured to have PerlIO, and therefore
2881           you cannot use IO layers.  To have PerlIO, Perl must be configured
2882           with 'useperlio'.
2883
2884       IO::Socket::atmark not implemented on this architecture
2885           (F) Your machine doesn't implement the sockatmark() functionality,
2886           neither as a system call nor an ioctl call (SIOCATMARK).
2887
2888       '%s' is an unknown bound type in regex; marked by <-- HERE in m/%s/
2889           (F) You used "\b{...}" or "\B{...}" and the "..." is not known to
2890           Perl.  The current valid ones are given in "\b{}, \b, \B{}, \B" in
2891           perlrebackslash.
2892
2893       %s is forbidden - matches null string many times in regex; marked by
2894       <-- HERE in m/%s/
2895           (F) The pattern you've specified might cause the regular expression
2896           to infinite loop so it is forbidden.  The <-- HERE shows
2897           whereabouts in the regular expression the problem was discovered.
2898           See perlre.
2899
2900       %s() isn't allowed on :utf8 handles
2901           (F) The sysread(), recv(), syswrite() and send() operators are not
2902           allowed on handles that have the ":utf8" layer, either explicitly,
2903           or implicitly, eg., with the ":encoding(UTF-16LE)" layer.
2904
2905           Previously sysread() and recv() currently use only the ":utf8" flag
2906           for the stream, ignoring the actual layers.  Since sysread() and
2907           recv() did no UTF-8 validation they can end up creating invalidly
2908           encoded scalars.
2909
2910           Similarly, syswrite() and send() used only the ":utf8" flag,
2911           otherwise ignoring any layers.  If the flag is set, both wrote the
2912           value UTF-8 encoded, even if the layer is some different encoding,
2913           such as the example above.
2914
2915           Ideally, all of these operators would completely ignore the ":utf8"
2916           state, working only with bytes, but this would result in silently
2917           breaking existing code.
2918
2919       "%s" is more clearly written simply as "%s" in regex; marked by
2920       <-- HERE in m/%s/
2921           (W regexp) (only under "use re 'strict'" or within "(?[...])")
2922
2923           You specified a character that has the given plainer way of writing
2924           it, and which is also portable to platforms running with different
2925           character sets.
2926
2927       $* is no longer supported as of Perl 5.30
2928           (F) The special variable $*, deprecated in older perls, was removed
2929           in 5.10.0, is no longer supported and is a fatal error as of Perl
2930           5.30.  In previous versions of perl the use of $* enabled or
2931           disabled multi-line matching within a string.
2932
2933           Instead of using $* you should use the "/m" (and maybe "/s") regexp
2934           modifiers.  You can enable "/m" for a lexical scope (even a whole
2935           file) with "use re '/m'".  (In older versions: when $* was set to a
2936           true value then all regular expressions behaved as if they were
2937           written using "/m".)
2938
2939           Use of this variable will be a fatal error in Perl 5.30.
2940
2941       $# is no longer supported as of Perl 5.30
2942           (F) The special variable $#, deprecated in older perls, was removed
2943           as of 5.10.0, is no longer supported and is a fatal error as of
2944           Perl 5.30.  You should use the printf/sprintf functions instead.
2945
2946       '%s' is not a code reference
2947           (W overload) The second (fourth, sixth, ...) argument of
2948           overload::constant needs to be a code reference.  Either an
2949           anonymous subroutine, or a reference to a subroutine.
2950
2951       '%s' is not an overloadable type
2952           (W overload) You tried to overload a constant type the overload
2953           package is unaware of.
2954
2955       isa is experimental
2956           (S experimental::isa) This warning is emitted if you use the
2957           ("isa") operator. This operator is currently experimental and its
2958           behaviour may change in future releases of Perl.
2959
2960       -i used with no filenames on the command line, reading from STDIN
2961           (S inplace) The "-i" option was passed on the command line,
2962           indicating that the script is intended to edit files in place, but
2963           no files were given.  This is usually a mistake, since editing
2964           STDIN in place doesn't make sense, and can be confusing because it
2965           can make perl look like it is hanging when it is really just trying
2966           to read from STDIN.  You should either pass a filename to edit, or
2967           remove "-i" from the command line.  See perlrun for more details.
2968
2969       Junk on end of regexp in regex m/%s/
2970           (P) The regular expression parser is confused.
2971
2972       \K not permitted in lookahead/lookbehind in regex; marked by <-- HERE
2973       in m/%s/
2974           (F) Your regular expression used "\K" in a lookahead or lookbehind
2975           assertion, which currently isn't permitted.
2976
2977           This may change in the future, see Support \K in lookarounds
2978           <https://github.com/Perl/perl5/issues/18134>.
2979
2980       Label not found for "last %s"
2981           (F) You named a loop to break out of, but you're not currently in a
2982           loop of that name, not even if you count where you were called
2983           from.  See "last" in perlfunc.
2984
2985       Label not found for "next %s"
2986           (F) You named a loop to continue, but you're not currently in a
2987           loop of that name, not even if you count where you were called
2988           from.  See "last" in perlfunc.
2989
2990       Label not found for "redo %s"
2991           (F) You named a loop to restart, but you're not currently in a loop
2992           of that name, not even if you count where you were called from.
2993           See "last" in perlfunc.
2994
2995       leaving effective %s failed
2996           (F) While under the "use filetest" pragma, switching the real and
2997           effective uids or gids failed.
2998
2999       length/code after end of string in unpack
3000           (F) While unpacking, the string buffer was already used up when an
3001           unpack length/code combination tried to obtain more data.  This
3002           results in an undefined value for the length.  See "pack" in
3003           perlfunc.
3004
3005       length() used on %s (did you mean "scalar(%s)"?)
3006           (W syntax) You used length() on either an array or a hash when you
3007           probably wanted a count of the items.
3008
3009           Array size can be obtained by doing:
3010
3011               scalar(@array);
3012
3013           The number of items in a hash can be obtained by doing:
3014
3015               scalar(keys %hash);
3016
3017       Lexing code attempted to stuff non-Latin-1 character into Latin-1 input
3018           (F) An extension is attempting to insert text into the current
3019           parse (using lex_stuff_pvn or similar), but tried to insert a
3020           character that couldn't be part of the current input.  This is an
3021           inherent pitfall of the stuffing mechanism, and one of the reasons
3022           to avoid it.  Where it is necessary to stuff, stuffing only plain
3023           ASCII is recommended.
3024
3025       Lexing code internal error (%s)
3026           (F) Lexing code supplied by an extension violated the lexer's API
3027           in a detectable way.
3028
3029       listen() on closed socket %s
3030           (W closed) You tried to do a listen on a closed socket.  Did you
3031           forget to check the return value of your socket() call?  See
3032           "listen" in perlfunc.
3033
3034       List form of piped open not implemented
3035           (F) On some platforms, notably Windows, the three-or-more-arguments
3036           form of "open" does not support pipes, such as "open($pipe, '|-',
3037           @args)".  Use the two-argument "open($pipe, '|prog arg1 arg2...')"
3038           form instead.
3039
3040       Literal vertical space in [] is illegal except under /x in regex;
3041       marked by <-- HERE in m/%s/
3042           (F) (only under "use re 'strict'" or within "(?[...])")
3043
3044           Likely you forgot the "/x" modifier or there was a typo in the
3045           pattern.  For example, did you really mean to match a form-feed?
3046           If so, all the ASCII vertical space control characters are
3047           representable by escape sequences which won't present such a
3048           jarring appearance as your pattern does when displayed.
3049
3050             \r    carriage return
3051             \f    form feed
3052             \n    line feed
3053             \cK   vertical tab
3054
3055       %s: loadable library and perl binaries are mismatched (got handshake
3056       key %p, needed %p)
3057           (P) A dynamic loading library ".so" or ".dll" was being loaded into
3058           the process that was built against a different build of perl than
3059           the said library was compiled against.  Reinstalling the XS module
3060           will likely fix this error.
3061
3062       Locale '%s' contains (at least) the following characters which have
3063       unexpected meanings: %s  The Perl program will use the expected
3064       meanings
3065           (W locale) You are using the named UTF-8 locale.  UTF-8 locales are
3066           expected to have very particular behavior, which most do.  This
3067           message arises when perl found some departures from the
3068           expectations, and is notifying you that the expected behavior
3069           overrides these differences.  In some cases the differences are
3070           caused by the locale definition being defective, but the most
3071           common causes of this warning are when there are ambiguities and
3072           conflicts in following the Standard, and the locale has chosen an
3073           approach that differs from Perl's.
3074
3075           One of these is because that, contrary to the claims, Unicode is
3076           not completely locale insensitive.  Turkish and some related
3077           languages have two types of "I" characters.  One is dotted in both
3078           upper- and lowercase, and the other is dotless in both cases.
3079           Unicode allows a locale to use either the Turkish rules, or the
3080           rules used in all other instances, where there is only one type of
3081           "I", which is dotless in the uppercase, and dotted in the lower.
3082           The perl core does not (yet) handle the Turkish case, and this
3083           message warns you of that.  Instead, the Unicode::Casing module
3084           allows you to mostly implement the Turkish casing rules.
3085
3086           The other common cause is for the characters
3087
3088            $ + < = > ^ ` | ~
3089
3090           These are problematic.  The C standard says that these should be
3091           considered punctuation in the C locale (and the POSIX standard
3092           defers to the C standard), and Unicode is generally considered a
3093           superset of the C locale.  But Unicode has added an extra category,
3094           "Symbol", and classifies these particular characters as being
3095           symbols.  Most UTF-8 locales have them treated as punctuation, so
3096           that ispunct(2) returns non-zero for them.  But a few locales have
3097           it return 0.   Perl takes the first approach, not using "ispunct()"
3098           at all (see Note [5] in perlrecharclass), and this message is
3099           raised to notify you that you are getting Perl's approach, not the
3100           locale's.
3101
3102       Locale '%s' may not work well.%s
3103           (W locale) You are using the named locale, which is a non-UTF-8
3104           one, and which perl has determined is not fully compatible with
3105           what it can handle.  The second %s gives a reason.
3106
3107           By far the most common reason is that the locale has characters in
3108           it that are represented by more than one byte.  The only such
3109           locales that Perl can handle are the UTF-8 locales.  Most likely
3110           the specified locale is a non-UTF-8 one for an East Asian language
3111           such as Chinese or Japanese.  If the locale is a superset of ASCII,
3112           the ASCII portion of it may work in Perl.
3113
3114           Some essentially obsolete locales that aren't supersets of ASCII,
3115           mainly those in ISO 646 or other 7-bit locales, such as ASMO 449,
3116           can also have problems, depending on what portions of the ASCII
3117           character set get changed by the locale and are also used by the
3118           program.  The warning message lists the determinable conflicting
3119           characters.
3120
3121           Note that not all incompatibilities are found.
3122
3123           If this happens to you, there's not much you can do except switch
3124           to use a different locale or use Encode to translate from the
3125           locale into UTF-8; if that's impracticable, you have been warned
3126           that some things may break.
3127
3128           This message is output once each time a bad locale is switched into
3129           within the scope of "use locale", or on the first possibly-affected
3130           operation if the "use locale" inherits a bad one.  It is not raised
3131           for any operations from the POSIX module.
3132
3133       localtime(%f) failed
3134           (W overflow) You called "localtime" with a number that it could not
3135           handle: too large, too small, or NaN.  The returned value is
3136           "undef".
3137
3138       localtime(%f) too large
3139           (W overflow) You called "localtime" with a number that was larger
3140           than it can reliably handle and "localtime" probably returned the
3141           wrong date.  This warning is also triggered with NaN (the special
3142           not-a-number value).
3143
3144       localtime(%f) too small
3145           (W overflow) You called "localtime" with a number that was smaller
3146           than it can reliably handle and "localtime" probably returned the
3147           wrong date.
3148
3149       Lookbehind longer than %d not implemented in regex m/%s/
3150           (F) There is currently a limit on the length of string which
3151           lookbehind can handle.  This restriction may be eased in a future
3152           release.
3153
3154       Lost precision when %s %f by 1
3155           (W imprecision) You attempted to increment or decrement a value by
3156           one, but the result is too large for the underlying floating point
3157           representation to store accurately. Hence, the target of "++" or
3158           "--" is increased or decreased by quite different value than one,
3159           such as zero (i.e. the target is unchanged) or two, due to
3160           rounding.  Perl issues this warning because it has already switched
3161           from integers to floating point when values are too large for
3162           integers, and now even floating point is insufficient.  You may
3163           wish to switch to using Math::BigInt explicitly.
3164
3165       lstat() on filehandle%s
3166           (W io) You tried to do an lstat on a filehandle.  What did you mean
3167           by that?  lstat() makes sense only on filenames.  (Perl did a
3168           fstat() instead on the filehandle.)
3169
3170       lvalue attribute %s already-defined subroutine
3171           (W misc) Although attributes.pm allows this, turning the lvalue
3172           attribute on or off on a Perl subroutine that is already defined
3173           does not always work properly.  It may or may not do what you want,
3174           depending on what code is inside the subroutine, with exact details
3175           subject to change between Perl versions.  Only do this if you
3176           really know what you are doing.
3177
3178       lvalue attribute ignored after the subroutine has been defined
3179           (W misc) Using the ":lvalue" declarative syntax to make a Perl
3180           subroutine an lvalue subroutine after it has been defined is not
3181           permitted.  To make the subroutine an lvalue subroutine, add the
3182           lvalue attribute to the definition, or put the "sub foo :lvalue;"
3183           declaration before the definition.
3184
3185           See also attributes.pm.
3186
3187       Magical list constants are not supported
3188           (F) You assigned a magical array to a stash element, and then tried
3189           to use the subroutine from the same slot.  You are asking Perl to
3190           do something it cannot do, details subject to change between Perl
3191           versions.
3192
3193       Malformed integer in [] in pack
3194           (F) Between the brackets enclosing a numeric repeat count only
3195           digits are permitted.  See "pack" in perlfunc.
3196
3197       Malformed integer in [] in unpack
3198           (F) Between the brackets enclosing a numeric repeat count only
3199           digits are permitted.  See "pack" in perlfunc.
3200
3201       Malformed PERLLIB_PREFIX
3202           (F) An error peculiar to OS/2.  PERLLIB_PREFIX should be of the
3203           form
3204
3205               prefix1;prefix2
3206
3207           or
3208               prefix1 prefix2
3209
3210           with nonempty prefix1 and prefix2.  If "prefix1" is indeed a prefix
3211           of a builtin library search path, prefix2 is substituted.  The
3212           error may appear if components are not found, or are too long.  See
3213           "PERLLIB_PREFIX" in perlos2.
3214
3215       Malformed prototype for %s: %s
3216           (F) You tried to use a function with a malformed prototype.  The
3217           syntax of function prototypes is given a brief compile-time check
3218           for obvious errors like invalid characters.  A more rigorous check
3219           is run when the function is called.  Perhaps the function's author
3220           was trying to write a subroutine signature but didn't enable that
3221           feature first ("use feature 'signatures'"), so the signature was
3222           instead interpreted as a bad prototype.
3223
3224       Malformed UTF-8 character%s
3225           (S utf8)(F) Perl detected a string that should be UTF-8, but didn't
3226           comply with UTF-8 encoding rules, or represents a code point whose
3227           ordinal integer value doesn't fit into the word size of the current
3228           platform (overflows).  Details as to the exact malformation are
3229           given in the variable, %s, part of the message.
3230
3231           One possible cause is that you set the UTF8 flag yourself for data
3232           that you thought to be in UTF-8 but it wasn't (it was for example
3233           legacy 8-bit data).  To guard against this, you can use
3234           "Encode::decode('UTF-8', ...)".
3235
3236           If you use the ":encoding(UTF-8)" PerlIO layer for input, invalid
3237           byte sequences are handled gracefully, but if you use ":utf8", the
3238           flag is set without validating the data, possibly resulting in this
3239           error message.
3240
3241           See also "Handling Malformed Data" in Encode.
3242
3243       Malformed UTF-8 returned by \N{%s} immediately after '%s'
3244           (F) The charnames handler returned malformed UTF-8.
3245
3246       Malformed UTF-8 string in "%s"
3247           (F) This message indicates a bug either in the Perl core or in XS
3248           code. Such code was trying to find out if a character, allegedly
3249           stored internally encoded as UTF-8, was of a given type, such as
3250           being punctuation or a digit.  But the character was not encoded in
3251           legal UTF-8.  The %s is replaced by a string that can be used by
3252           knowledgeable people to determine what the type being checked
3253           against was.
3254
3255           Passing malformed strings was deprecated in Perl 5.18, and became
3256           fatal in Perl 5.26.
3257
3258       Malformed UTF-8 string in '%c' format in unpack
3259           (F) You tried to unpack something that didn't comply with UTF-8
3260           encoding rules and perl was unable to guess how to make more
3261           progress.
3262
3263       Malformed UTF-8 string in pack
3264           (F) You tried to pack something that didn't comply with UTF-8
3265           encoding rules and perl was unable to guess how to make more
3266           progress.
3267
3268       Malformed UTF-8 string in unpack
3269           (F) You tried to unpack something that didn't comply with UTF-8
3270           encoding rules and perl was unable to guess how to make more
3271           progress.
3272
3273       Malformed UTF-16 surrogate
3274           (F) Perl thought it was reading UTF-16 encoded character data but
3275           while doing it Perl met a malformed Unicode surrogate.
3276
3277       Mandatory parameter follows optional parameter
3278           (F) In a subroutine signature, you wrote something like "$a =
3279           undef, $b", making an earlier parameter optional and a later one
3280           mandatory.  Parameters are filled from left to right, so it's
3281           impossible for the caller to omit an earlier one and pass a later
3282           one.  If you want to act as if the parameters are filled from right
3283           to left, declare the rightmost optional and then shuffle the
3284           parameters around in the subroutine's body.
3285
3286       Matched non-Unicode code point 0x%X against Unicode property; may not
3287       be portable
3288           (S non_unicode) Perl allows strings to contain a superset of
3289           Unicode code points; each code point may be as large as what is
3290           storable in a signed integer on your system, but these may not be
3291           accepted by other languages/systems.  This message occurs when you
3292           matched a string containing such a code point against a regular
3293           expression pattern, and the code point was matched against a
3294           Unicode property, "\p{...}" or "\P{...}".  Unicode properties are
3295           only defined on Unicode code points, so the result of this match is
3296           undefined by Unicode, but Perl (starting in v5.20) treats non-
3297           Unicode code points as if they were typical unassigned Unicode
3298           ones, and matched this one accordingly.  Whether a given property
3299           matches these code points or not is specified in "Properties
3300           accessible through \p{} and \P{}" in perluniprops.
3301
3302           This message is suppressed (unless it has been made fatal) if it is
3303           immaterial to the results of the match if the code point is Unicode
3304           or not.  For example, the property "\p{ASCII_Hex_Digit}" only can
3305           match the 22 characters "[0-9A-Fa-f]", so obviously all other code
3306           points, Unicode or not, won't match it.  (And "\P{ASCII_Hex_Digit}"
3307           will match every code point except these 22.)
3308
3309           Getting this message indicates that the outcome of the match
3310           arguably should have been the opposite of what actually happened.
3311           If you think that is the case, you may wish to make the
3312           "non_unicode" warnings category fatal; if you agree with Perl's
3313           decision, you may wish to turn off this category.
3314
3315           See "Beyond Unicode code points" in perlunicode for more
3316           information.
3317
3318       %s matches null string many times in regex; marked by <-- HERE in m/%s/
3319           (W regexp) The pattern you've specified would be an infinite loop
3320           if the regular expression engine didn't specifically check for
3321           that.  The <-- HERE shows whereabouts in the regular expression the
3322           problem was discovered.  See perlre.
3323
3324       Maximal count of pending signals (%u) exceeded
3325           (F) Perl aborted due to too high a number of signals pending.  This
3326           usually indicates that your operating system tried to deliver
3327           signals too fast (with a very high priority), starving the perl
3328           process from resources it would need to reach a point where it can
3329           process signals safely.  (See "Deferred Signals (Safe Signals)" in
3330           perlipc.)
3331
3332       "%s" may clash with future reserved word
3333           (W) This warning may be due to running a perl5 script through a
3334           perl4 interpreter, especially if the word that is being warned
3335           about is "use" or "my".
3336
3337       '%' may not be used in pack
3338           (F) You can't pack a string by supplying a checksum, because the
3339           checksumming process loses information, and you can't go the other
3340           way.  See "unpack" in perlfunc.
3341
3342       Method for operation %s not found in package %s during blessing
3343           (F) An attempt was made to specify an entry in an overloading table
3344           that doesn't resolve to a valid subroutine.  See overload.
3345
3346       Method %s not permitted
3347           See "500 Server error".
3348
3349       Might be a runaway multi-line %s string starting on line %d
3350           (S) An advisory indicating that the previous error may have been
3351           caused by a missing delimiter on a string or pattern, because it
3352           eventually ended earlier on the current line.
3353
3354       Misplaced _ in number
3355           (W syntax) An underscore (underbar) in a numeric constant did not
3356           separate two digits.
3357
3358       Missing argument for %n in %s
3359           (F) A %n was used in a format string with no corresponding argument
3360           for perl to write the current string length to.
3361
3362       Missing argument in %s
3363           (W missing) You called a function with fewer arguments than other
3364           arguments you supplied indicated would be needed.
3365
3366           Currently only emitted when a printf-type format required more
3367           arguments than were supplied, but might be used in the future for
3368           other cases where we can statically determine that arguments to
3369           functions are missing, e.g. for the "pack" in perlfunc function.
3370
3371       Missing argument to -%c
3372           (F) The argument to the indicated command line switch must follow
3373           immediately after the switch, without intervening spaces.
3374
3375       Missing braces on \N{}
3376       Missing braces on \N{} in regex; marked by <-- HERE in m/%s/
3377           (F) Wrong syntax of character name literal "\N{charname}" within
3378           double-quotish context.  This can also happen when there is a space
3379           (or comment) between the "\N" and the "{" in a regex with the "/x"
3380           modifier.  This modifier does not change the requirement that the
3381           brace immediately follow the "\N".
3382
3383       Missing braces on \o{}
3384           (F) A "\o" must be followed immediately by a "{" in double-quotish
3385           context.
3386
3387       Missing comma after first argument to %s function
3388           (F) While certain functions allow you to specify a filehandle or an
3389           "indirect object" before the argument list, this ain't one of them.
3390
3391       Missing command in piped open
3392           (W pipe) You used the "open(FH, "| command")" or "open(FH, "command
3393           |")" construction, but the command was missing or blank.
3394
3395       Missing control char name in \c
3396           (F) A double-quoted string ended with "\c", without the required
3397           control character name.
3398
3399       Missing ']' in prototype for %s : %s
3400           (W illegalproto) A grouping was started with "[" but never closed
3401           with "]".
3402
3403       Missing name in "%s sub"
3404           (F) The syntax for lexically scoped subroutines requires that they
3405           have a name with which they can be found.
3406
3407       Missing $ on loop variable
3408           (F) Apparently you've been programming in csh too much.  Variables
3409           are always mentioned with the $ in Perl, unlike in the shells,
3410           where it can vary from one line to the next.
3411
3412       (Missing operator before %s?)
3413           (S syntax) This is an educated guess made in conjunction with the
3414           message "%s found where operator expected".  Often the missing
3415           operator is a comma.
3416
3417       Missing or undefined argument to %s
3418           (F) You tried to call require or do with no argument or with an
3419           undefined value as an argument.  Require expects either a package
3420           name or a file-specification as an argument; do expects a filename.
3421           See "require EXPR" in perlfunc and "do EXPR" in perlfunc.
3422
3423       Missing right brace on \%c{} in regex; marked by <-- HERE in m/%s/
3424           (F) Missing right brace in "\x{...}", "\p{...}", "\P{...}", or
3425           "\N{...}".
3426
3427       Missing right brace on \N{}
3428       Missing right brace on \N{} or unescaped left brace after \N
3429           (F) "\N" has two meanings.
3430
3431           The traditional one has it followed by a name enclosed in braces,
3432           meaning the character (or sequence of characters) given by that
3433           name.  Thus "\N{ASTERISK}" is another way of writing "*", valid in
3434           both double-quoted strings and regular expression patterns.  In
3435           patterns, it doesn't have the meaning an unescaped "*" does.
3436
3437           Starting in Perl 5.12.0, "\N" also can have an additional meaning
3438           (only) in patterns, namely to match a non-newline character.  (This
3439           is short for "[^\n]", and like "." but is not affected by the "/s"
3440           regex modifier.)
3441
3442           This can lead to some ambiguities.  When "\N" is not followed
3443           immediately by a left brace, Perl assumes the "[^\n]" meaning.
3444           Also, if the braces form a valid quantifier such as "\N{3}" or
3445           "\N{5,}", Perl assumes that this means to match the given quantity
3446           of non-newlines (in these examples, 3; and 5 or more,
3447           respectively).  In all other case, where there is a "\N{" and a
3448           matching "}", Perl assumes that a character name is desired.
3449
3450           However, if there is no matching "}", Perl doesn't know if it was
3451           mistakenly omitted, or if "[^\n]{" was desired, and raises this
3452           error.  If you meant the former, add the right brace; if you meant
3453           the latter, escape the brace with a backslash, like so: "\N\{"
3454
3455       Missing right curly or square bracket
3456           (F) The lexer counted more opening curly or square brackets than
3457           closing ones.  As a general rule, you'll find it's missing near the
3458           place you were last editing.
3459
3460       (Missing semicolon on previous line?)
3461           (S syntax) This is an educated guess made in conjunction with the
3462           message "%s found where operator expected".  Don't automatically
3463           put a semicolon on the previous line just because you saw this
3464           message.
3465
3466       Modification of a read-only value attempted
3467           (F) You tried, directly or indirectly, to change the value of a
3468           constant.  You didn't, of course, try "2 = 1", because the compiler
3469           catches that.  But an easy way to do the same thing is:
3470
3471               sub mod { $_[0] = 1 }
3472               mod(2);
3473
3474           Another way is to assign to a substr() that's off the end of the
3475           string.
3476
3477           Yet another way is to assign to a "foreach" loop VAR when VAR is
3478           aliased to a constant in the look LIST:
3479
3480               $x = 1;
3481               foreach my $n ($x, 2) {
3482                   $n *= 2; # modifies the $x, but fails on attempt to
3483               }            # modify the 2
3484
3485           PerlIO::scalar will also produce this message as a warning if you
3486           attempt to open a read-only scalar for writing.
3487
3488       Modification of non-creatable array value attempted, %s
3489           (F) You tried to make an array value spring into existence, and the
3490           subscript was probably negative, even counting from end of the
3491           array backwards.
3492
3493       Modification of non-creatable hash value attempted, %s
3494           (P) You tried to make a hash value spring into existence, and it
3495           couldn't be created for some peculiar reason.
3496
3497       Module name must be constant
3498           (F) Only a bare module name is allowed as the first argument to a
3499           "use".
3500
3501       Module name required with -%c option
3502           (F) The "-M" or "-m" options say that Perl should load some module,
3503           but you omitted the name of the module.  Consult perlrun for full
3504           details about "-M" and "-m".
3505
3506       More than one argument to '%s' open
3507           (F) The "open" function has been asked to open multiple files.
3508           This can happen if you are trying to open a pipe to a command that
3509           takes a list of arguments, but have forgotten to specify a piped
3510           open mode.  See "open" in perlfunc for details.
3511
3512       mprotect for COW string %p %u failed with %d
3513           (S) You compiled perl with -DPERL_DEBUG_READONLY_COW (see "Copy on
3514           Write" in perlguts), but a shared string buffer could not be made
3515           read-only.
3516
3517       mprotect for %p %u failed with %d
3518           (S) You compiled perl with -DPERL_DEBUG_READONLY_OPS (see
3519           perlhacktips), but an op tree could not be made read-only.
3520
3521       mprotect RW for COW string %p %u failed with %d
3522           (S) You compiled perl with -DPERL_DEBUG_READONLY_COW (see "Copy on
3523           Write" in perlguts), but a read-only shared string buffer could not
3524           be made mutable.
3525
3526       mprotect RW for %p %u failed with %d
3527           (S) You compiled perl with -DPERL_DEBUG_READONLY_OPS (see
3528           perlhacktips), but a read-only op tree could not be made mutable
3529           before freeing the ops.
3530
3531       msg%s not implemented
3532           (F) You don't have System V message IPC on your system.
3533
3534       Multidimensional hash lookup is disabled
3535           (F) You supplied a list of subscripts to a hash lookup under "no
3536           feature "multidimensional";", eg:
3537
3538             $z = $foo{$x, $y};
3539
3540           which by default acts like:
3541
3542             $z = $foo{join($;, $x, $y)};
3543
3544       Multidimensional syntax %s not supported
3545           (W syntax) Multidimensional arrays aren't written like $foo[1,2,3].
3546           They're written like $foo[1][2][3], as in C.
3547
3548       Multiple slurpy parameters not allowed
3549           (F) In subroutine signatures, a slurpy parameter ("@" or "%") must
3550           be the last parameter, and there must not be more than one of them;
3551           for example:
3552
3553               sub foo ($a, @b)    {} # legal
3554               sub foo ($a, @b, %) {} # invalid
3555
3556       '/' must follow a numeric type in unpack
3557           (F) You had an unpack template that contained a '/', but this did
3558           not follow some unpack specification producing a numeric value.
3559           See "pack" in perlfunc.
3560
3561       %s must not be a named sequence in transliteration operator
3562           (F) Transliteration ("tr///" and "y///") transliterates individual
3563           characters.  But a named sequence by definition is more than an
3564           individual character, and hence doing this operation on it doesn't
3565           make sense.
3566
3567       "my sub" not yet implemented
3568           (F) Lexically scoped subroutines are not yet implemented.  Don't
3569           try that yet.
3570
3571       "my" subroutine %s can't be in a package
3572           (F) Lexically scoped subroutines aren't in a package, so it doesn't
3573           make sense to try to declare one with a package qualifier on the
3574           front.
3575
3576       "my %s" used in sort comparison
3577           (W syntax) The package variables $a and $b are used for sort
3578           comparisons.  You used $a or $b in as an operand to the "<=>" or
3579           "cmp" operator inside a sort comparison block, and the variable had
3580           earlier been declared as a lexical variable.  Either qualify the
3581           sort variable with the package name, or rename the lexical
3582           variable.
3583
3584       "my" variable %s can't be in a package
3585           (F) Lexically scoped variables aren't in a package, so it doesn't
3586           make sense to try to declare one with a package qualifier on the
3587           front.  Use local() if you want to localize a package variable.
3588
3589       Name "%s::%s" used only once: possible typo
3590           (W once) Typographical errors often show up as unique variable
3591           names.  If you had a good reason for having a unique name, then
3592           just mention it again somehow to suppress the message.  The "our"
3593           declaration is also provided for this purpose.
3594
3595           NOTE: This warning detects package symbols that have been used only
3596           once.  This means lexical variables will never trigger this
3597           warning.  It also means that all of the package variables $c, @c,
3598           %c, as well as *c, &c, sub c{}, c(), and c (the filehandle or
3599           format) are considered the same; if a program uses $c only once but
3600           also uses any of the others it will not trigger this warning.
3601           Symbols beginning with an underscore and symbols using special
3602           identifiers (q.v. perldata) are exempt from this warning.
3603
3604       Need exactly 3 octal digits in regex; marked by <-- HERE in m/%s/
3605           (F) Within "(?[   ])", all constants interpreted as octal need to
3606           be exactly 3 digits long.  This helps catch some ambiguities.  If
3607           your constant is too short, add leading zeros, like
3608
3609            (?[ [ \078 ] ])     # Syntax error!
3610            (?[ [ \0078 ] ])    # Works
3611            (?[ [ \007 8 ] ])   # Clearer
3612
3613           The maximum number this construct can express is "\777".  If you
3614           need a larger one, you need to use \o{} instead.  If you meant two
3615           separate things, you need to separate them:
3616
3617            (?[ [ \7776 ] ])        # Syntax error!
3618            (?[ [ \o{7776} ] ])     # One meaning
3619            (?[ [ \777 6 ] ])       # Another meaning
3620            (?[ [ \777 \006 ] ])    # Still another
3621
3622       Negative '/' count in unpack
3623           (F) The length count obtained from a length/code unpack operation
3624           was negative.  See "pack" in perlfunc.
3625
3626       Negative length
3627           (F) You tried to do a read/write/send/recv operation with a buffer
3628           length that is less than 0.  This is difficult to imagine.
3629
3630       Negative offset to vec in lvalue context
3631           (F) When "vec" is called in an lvalue context, the second argument
3632           must be greater than or equal to zero.
3633
3634       Negative repeat count does nothing
3635           (W numeric) You tried to execute the "x" repetition operator fewer
3636           than 0 times, which doesn't make sense.
3637
3638       Nested quantifiers in regex; marked by <-- HERE in m/%s/
3639           (F) You can't quantify a quantifier without intervening
3640           parentheses.  So things like ** or +* or ?* are illegal.  The
3641           <-- HERE shows whereabouts in the regular expression the problem
3642           was discovered.
3643
3644           Note that the minimal matching quantifiers, "*?", "+?", and "??"
3645           appear to be nested quantifiers, but aren't.  See perlre.
3646
3647       %s never introduced
3648           (S internal) The symbol in question was declared but somehow went
3649           out of scope before it could possibly have been used.
3650
3651       next::method/next::can/maybe::next::method cannot find enclosing method
3652           (F) "next::method" needs to be called within the context of a real
3653           method in a real package, and it could not find such a context.
3654           See mro.
3655
3656       \N in a character class must be a named character: \N{...} in regex;
3657       marked by <-- HERE in m/%s/
3658           (F) The new (as of Perl 5.12) meaning of "\N" as "[^\n]" is not
3659           valid in a bracketed character class, for the same reason that "."
3660           in a character class loses its specialness: it matches almost
3661           everything, which is probably not what you want.
3662
3663       \N{} here is restricted to one character in regex; marked by <-- HERE
3664       in m/%s/
3665           (F) Named Unicode character escapes ("\N{...}") may return a multi-
3666           character sequence.  Even though a character class is supposed to
3667           match just one character of input, perl will match the whole thing
3668           correctly, except under certain conditions.  These currently are
3669
3670           When the class is inverted ("[^...]")
3671               The mathematically logical behavior for what matches when
3672               inverting is very different from what people expect, so we have
3673               decided to forbid it.
3674
3675           The escape is the beginning or final end point of a range
3676               Similarly unclear is what should be generated when the
3677               "\N{...}" is used as one of the end points of the range, such
3678               as in
3679
3680                [\x{41}-\N{ARABIC SEQUENCE YEH WITH HAMZA ABOVE WITH AE}]
3681
3682               What is meant here is unclear, as the "\N{...}" escape is a
3683               sequence of code points, so this is made an error.
3684
3685           In a regex set
3686               The syntax "(?[   ])" in a regular expression yields a list of
3687               single code points, none can be a sequence.
3688
3689       No %s allowed while running setuid
3690           (F) Certain operations are deemed to be too insecure for a setuid
3691           or setgid script to even be allowed to attempt.  Generally speaking
3692           there will be another way to do what you want that is, if not
3693           secure, at least securable.  See perlsec.
3694
3695       No code specified for -%c
3696           (F) Perl's -e and -E command-line options require an argument.  If
3697           you want to run an empty program, pass the empty string as a
3698           separate argument or run a program consisting of a single 0 or 1:
3699
3700               perl -e ""
3701               perl -e0
3702               perl -e1
3703
3704       No comma allowed after %s
3705           (F) A list operator that has a filehandle or "indirect object" is
3706           not allowed to have a comma between that and the following
3707           arguments.  Otherwise it'd be just another one of the arguments.
3708
3709           One possible cause for this is that you expected to have imported a
3710           constant to your name space with use or import while no such
3711           importing took place, it may for example be that your operating
3712           system does not support that particular constant.  Hopefully you
3713           did use an explicit import list for the constants you expect to
3714           see; please see "use" in perlfunc and "import" in perlfunc.  While
3715           an explicit import list would probably have caught this error
3716           earlier it naturally does not remedy the fact that your operating
3717           system still does not support that constant.  Maybe you have a typo
3718           in the constants of the symbol import list of use or import or in
3719           the constant name at the line where this error was triggered?
3720
3721       No command into which to pipe on command line
3722           (F) An error peculiar to VMS.  Perl handles its own command line
3723           redirection, and found a '|' at the end of the command line, so it
3724           doesn't know where you want to pipe the output from this command.
3725
3726       No DB::DB routine defined
3727           (F) The currently executing code was compiled with the -d switch,
3728           but for some reason the current debugger (e.g. perl5db.pl or a
3729           "Devel::" module) didn't define a routine to be called at the
3730           beginning of each statement.
3731
3732       No dbm on this machine
3733           (P) This is counted as an internal error, because every machine
3734           should supply dbm nowadays, because Perl comes with SDBM.  See
3735           SDBM_File.
3736
3737       No DB::sub routine defined
3738           (F) The currently executing code was compiled with the -d switch,
3739           but for some reason the current debugger (e.g. perl5db.pl or a
3740           "Devel::" module) didn't define a "DB::sub" routine to be called at
3741           the beginning of each ordinary subroutine call.
3742
3743       No digits found for %s literal
3744           (F) No hexadecimal digits were found following "0x" or no binary
3745           digits were found following "0b".
3746
3747       No directory specified for -I
3748           (F) The -I command-line switch requires a directory name as part of
3749           the same argument.  Use -Ilib, for instance.  -I lib won't work.
3750
3751       No error file after 2> or 2>> on command line
3752           (F) An error peculiar to VMS.  Perl handles its own command line
3753           redirection, and found a '2>' or a '2>>' on the command line, but
3754           can't find the name of the file to which to write data destined for
3755           stderr.
3756
3757       No group ending character '%c' found in template
3758           (F) A pack or unpack template has an opening '(' or '[' without its
3759           matching counterpart.  See "pack" in perlfunc.
3760
3761       No input file after < on command line
3762           (F) An error peculiar to VMS.  Perl handles its own command line
3763           redirection, and found a '<' on the command line, but can't find
3764           the name of the file from which to read data for stdin.
3765
3766       No next::method '%s' found for %s
3767           (F) "next::method" found no further instances of this method name
3768           in the remaining packages of the MRO of this class.  If you don't
3769           want it throwing an exception, use "maybe::next::method" or
3770           "next::can".  See mro.
3771
3772       Non-finite repeat count does nothing
3773           (W numeric) You tried to execute the "x" repetition operator "Inf"
3774           (or "-Inf") or "NaN" times, which doesn't make sense.
3775
3776       Non-hex character in regex; marked by <-- HERE in m/%s/
3777           (F) In a regular expression, there was a non-hexadecimal character
3778           where a hex one was expected, like
3779
3780            (?[ [ \xDG ] ])
3781            (?[ [ \x{DEKA} ] ])
3782
3783       Non-hex character '%c' terminates \x early.  Resolved as "%s"
3784           (W digit) In parsing a hexadecimal numeric constant, a character
3785           was unexpectedly encountered that isn't hexadecimal.  The resulting
3786           value is as indicated.
3787
3788           Note that, within braces, every character starting with the first
3789           non-hexadecimal up to the ending brace is ignored.
3790
3791       Non-octal character in regex; marked by <-- HERE in m/%s/
3792           (F) In a regular expression, there was a non-octal character where
3793           an octal one was expected, like
3794
3795            (?[ [ \o{1278} ] ])
3796
3797       Non-octal character '%c' terminates \o early.  Resolved as "%s"
3798           (W digit) In parsing an octal numeric constant, a character was
3799           unexpectedly encountered that isn't octal.  The resulting value is
3800           as indicated.
3801
3802           When not using "\o{...}", you wrote something like "\08", or "\179"
3803           in a double-quotish string.  The resolution is as indicated, with
3804           all but the last digit treated as a single character, specified in
3805           octal.  The last digit is the next character in the string.  To
3806           tell Perl that this is indeed what you want, you can use the "\o{
3807           }" syntax, or use exactly three digits to specify the octal for the
3808           character.
3809
3810           Note that, within braces, every character starting with the first
3811           non-octal up to the ending brace is ignored.
3812
3813       "no" not allowed in expression
3814           (F) The "no" keyword is recognized and executed at compile time,
3815           and returns no useful value.  See perlmod.
3816
3817       Non-string passed as bitmask
3818           (W misc) A number has been passed as a bitmask argument to
3819           select().  Use the vec() function to construct the file descriptor
3820           bitmasks for select.  See "select" in perlfunc.
3821
3822       No output file after > on command line
3823           (F) An error peculiar to VMS.  Perl handles its own command line
3824           redirection, and found a lone '>' at the end of the command line,
3825           so it doesn't know where you wanted to redirect stdout.
3826
3827       No output file after > or >> on command line
3828           (F) An error peculiar to VMS.  Perl handles its own command line
3829           redirection, and found a '>' or a '>>' on the command line, but
3830           can't find the name of the file to which to write data destined for
3831           stdout.
3832
3833       No package name allowed for subroutine %s in "our"
3834       No package name allowed for variable %s in "our"
3835           (F) Fully qualified subroutine and variable names are not allowed
3836           in "our" declarations, because that doesn't make much sense under
3837           existing rules.  Such syntax is reserved for future extensions.
3838
3839       No Perl script found in input
3840           (F) You called "perl -x", but no line was found in the file
3841           beginning with #! and containing the word "perl".
3842
3843       No setregid available
3844           (F) Configure didn't find anything resembling the setregid() call
3845           for your system.
3846
3847       No setreuid available
3848           (F) Configure didn't find anything resembling the setreuid() call
3849           for your system.
3850
3851       No such class %s
3852           (F) You provided a class qualifier in a "my", "our" or "state"
3853           declaration, but this class doesn't exist at this point in your
3854           program.
3855
3856       No such class field "%s" in variable %s of type %s
3857           (F) You tried to access a key from a hash through the indicated
3858           typed variable but that key is not allowed by the package of the
3859           same type.  The indicated package has restricted the set of allowed
3860           keys using the fields pragma.
3861
3862       No such hook: %s
3863           (F) You specified a signal hook that was not recognized by Perl.
3864           Currently, Perl accepts "__DIE__" and "__WARN__" as valid signal
3865           hooks.
3866
3867       No such pipe open
3868           (P) An error peculiar to VMS.  The internal routine my_pclose()
3869           tried to close a pipe which hadn't been opened.  This should have
3870           been caught earlier as an attempt to close an unopened filehandle.
3871
3872       No such signal: SIG%s
3873           (W signal) You specified a signal name as a subscript to %SIG that
3874           was not recognized.  Say "kill -l" in your shell to see the valid
3875           signal names on your system.
3876
3877       No Unicode property value wildcard matches:
3878           (W regexp) You specified a wildcard for a Unicode property value,
3879           but there is no property value in the current Unicode release that
3880           matches it.  Check your spelling.
3881
3882       Not a CODE reference
3883           (F) Perl was trying to evaluate a reference to a code value (that
3884           is, a subroutine), but found a reference to something else instead.
3885           You can use the ref() function to find out what kind of ref it
3886           really was.  See also perlref.
3887
3888       Not a GLOB reference
3889           (F) Perl was trying to evaluate a reference to a "typeglob" (that
3890           is, a symbol table entry that looks like *foo), but found a
3891           reference to something else instead.  You can use the ref()
3892           function to find out what kind of ref it really was.  See perlref.
3893
3894       Not a HASH reference
3895           (F) Perl was trying to evaluate a reference to a hash value, but
3896           found a reference to something else instead.  You can use the ref()
3897           function to find out what kind of ref it really was.  See perlref.
3898
3899       '#' not allowed immediately following a sigil in a subroutine signature
3900           (F) In a subroutine signature definition, a comment following a
3901           sigil ("$", "@" or "%"), needs to be separated by whitespace or a
3902           comma etc., in particular to avoid confusion with the $# variable.
3903           For example:
3904
3905               # bad
3906               sub f ($# ignore first arg
3907                      , $b) {}
3908               # good
3909               sub f ($, # ignore first arg
3910                      $b) {}
3911
3912       Not an ARRAY reference
3913           (F) Perl was trying to evaluate a reference to an array value, but
3914           found a reference to something else instead.  You can use the ref()
3915           function to find out what kind of ref it really was.  See perlref.
3916
3917       Not a SCALAR reference
3918           (F) Perl was trying to evaluate a reference to a scalar value, but
3919           found a reference to something else instead.  You can use the ref()
3920           function to find out what kind of ref it really was.  See perlref.
3921
3922       Not a subroutine reference
3923           (F) Perl was trying to evaluate a reference to a code value (that
3924           is, a subroutine), but found a reference to something else instead.
3925           You can use the ref() function to find out what kind of ref it
3926           really was.  See also perlref.
3927
3928       Not a subroutine reference in overload table
3929           (F) An attempt was made to specify an entry in an overloading table
3930           that doesn't somehow point to a valid subroutine.  See overload.
3931
3932       Not enough arguments for %s
3933           (F) The function requires more arguments than you specified.
3934
3935       Not enough format arguments
3936           (W syntax) A format specified more picture fields than the next
3937           line supplied.  See perlform.
3938
3939       %s: not found
3940           (A) You've accidentally run your script through the Bourne shell
3941           instead of Perl.  Check the #! line, or manually feed your script
3942           into Perl yourself.
3943
3944       no UTC offset information; assuming local time is UTC
3945           (S) A warning peculiar to VMS.  Perl was unable to find the local
3946           timezone offset, so it's assuming that local system time is
3947           equivalent to UTC.  If it's not, define the logical name
3948           SYS$TIMEZONE_DIFFERENTIAL to translate to the number of seconds
3949           which need to be added to UTC to get local time.
3950
3951       NULL OP IN RUN
3952           (S debugging) Some internal routine called run() with a null opcode
3953           pointer.
3954
3955       Null picture in formline
3956           (F) The first argument to formline must be a valid format picture
3957           specification.  It was found to be empty, which probably means you
3958           supplied it an uninitialized value.  See perlform.
3959
3960       Null realloc
3961           (P) An attempt was made to realloc NULL.
3962
3963       NULL regexp argument
3964           (P) The internal pattern matching routines blew it big time.
3965
3966       NULL regexp parameter
3967           (P) The internal pattern matching routines are out of their gourd.
3968
3969       Number too long
3970           (F) Perl limits the representation of decimal numbers in programs
3971           to about 250 characters.  You've exceeded that length.  Future
3972           versions of Perl are likely to eliminate this arbitrary limitation.
3973           In the meantime, try using scientific notation (e.g. "1e6" instead
3974           of "1_000_000").
3975
3976       Number with no digits
3977           (F) Perl was looking for a number but found nothing that looked
3978           like a number.  This happens, for example with "\o{}", with no
3979           number between the braces.
3980
3981       Numeric format result too large
3982           (F) The length of the result of a numeric format supplied to
3983           sprintf() or printf() would have been too large for the underlying
3984           C function to report.  This limit is typically 2GB.
3985
3986       Numeric variables with more than one digit may not start with '0'
3987           (F) The only numeric variable which is allowed to start with a 0 is
3988           $0, and you mentioned a variable that starts with 0 that has more
3989           than one digit. You probably want to remove the leading 0, or if
3990           the intent was to express a variable name in octal you should
3991           convert to decimal.
3992
3993       Octal number > 037777777777 non-portable
3994           (W portable) The octal number you specified is larger than 2**32-1
3995           (4294967295) and therefore non-portable between systems.  See
3996           perlport for more on portability concerns.
3997
3998       Odd name/value argument for subroutine '%s'
3999           (F) A subroutine using a slurpy hash parameter in its signature
4000           received an odd number of arguments to populate the hash.  It
4001           requires the arguments to be paired, with the same number of keys
4002           as values.  The caller of the subroutine is presumably at fault.
4003
4004           The message attempts to include the name of the called subroutine.
4005           If the subroutine has been aliased, the subroutine's original name
4006           will be shown, regardless of what name the caller used.
4007
4008       Odd number of arguments for overload::constant
4009           (W overload) The call to overload::constant contained an odd number
4010           of arguments.  The arguments should come in pairs.
4011
4012       Odd number of elements in anonymous hash
4013           (W misc) You specified an odd number of elements to initialize a
4014           hash, which is odd, because hashes come in key/value pairs.
4015
4016       Odd number of elements in hash assignment
4017           (W misc) You specified an odd number of elements to initialize a
4018           hash, which is odd, because hashes come in key/value pairs.
4019
4020       Offset outside string
4021           (F)(W layer) You tried to do a read/write/send/recv/seek operation
4022           with an offset pointing outside the buffer.  This is difficult to
4023           imagine.  The sole exceptions to this are that zero padding will
4024           take place when going past the end of the string when either
4025           "sysread()"ing a file, or when seeking past the end of a scalar
4026           opened for I/O (in anticipation of future reads and to imitate the
4027           behavior with real files).
4028
4029       Old package separator used in string
4030           (W syntax) You used the old package separator, "'", in a variable
4031           named inside a double-quoted string; e.g., "In $name's house".
4032           This is equivalent to "In $name::s house".  If you meant the
4033           former, put a backslash before the apostrophe ("In $name\'s
4034           house").
4035
4036       %s() on unopened %s
4037           (W unopened) An I/O operation was attempted on a filehandle that
4038           was never initialized.  You need to do an open(), a sysopen(), or a
4039           socket() call, or call a constructor from the FileHandle package.
4040
4041       -%s on unopened filehandle %s
4042           (W unopened) You tried to invoke a file test operator on a
4043           filehandle that isn't open.  Check your control flow.  See also
4044           "-X" in perlfunc.
4045
4046       oops: oopsAV
4047           (S internal) An internal warning that the grammar is screwed up.
4048
4049       oops: oopsHV
4050           (S internal) An internal warning that the grammar is screwed up.
4051
4052       Operand with no preceding operator in regex; marked by <-- HERE in
4053       m/%s/
4054           (F) You wrote something like
4055
4056            (?[ \p{Digit} \p{Thai} ])
4057
4058           There are two operands, but no operator giving how you want to
4059           combine them.
4060
4061       Operation "%s": no method found, %s
4062           (F) An attempt was made to perform an overloaded operation for
4063           which no handler was defined.  While some handlers can be
4064           autogenerated in terms of other handlers, there is no default
4065           handler for any operation, unless the "fallback" overloading key is
4066           specified to be true.  See overload.
4067
4068       Operation "%s" returns its argument for non-Unicode code point 0x%X
4069           (S non_unicode) You performed an operation requiring Unicode rules
4070           on a code point that is not in Unicode, so what it should do is not
4071           defined.  Perl has chosen to have it do nothing, and warn you.
4072
4073           If the operation shown is "ToFold", it means that case-insensitive
4074           matching in a regular expression was done on the code point.
4075
4076           If you know what you are doing you can turn off this warning by "no
4077           warnings 'non_unicode';".
4078
4079       Operation "%s" returns its argument for UTF-16 surrogate U+%X
4080           (S surrogate) You performed an operation requiring Unicode rules on
4081           a Unicode surrogate.  Unicode frowns upon the use of surrogates for
4082           anything but storing strings in UTF-16, but rules are (reluctantly)
4083           defined for the surrogates, and they are to do nothing for this
4084           operation.  Because the use of surrogates can be dangerous, Perl
4085           warns.
4086
4087           If the operation shown is "ToFold", it means that case-insensitive
4088           matching in a regular expression was done on the code point.
4089
4090           If you know what you are doing you can turn off this warning by "no
4091           warnings 'surrogate';".
4092
4093       Operator or semicolon missing before %s
4094           (S ambiguous) You used a variable or subroutine call where the
4095           parser was expecting an operator.  The parser has assumed you
4096           really meant to use an operator, but this is highly likely to be
4097           incorrect.  For example, if you say "*foo *foo" it will be
4098           interpreted as if you said "*foo * 'foo'".
4099
4100       Optional parameter lacks default expression
4101           (F) In a subroutine signature, you wrote something like "$a =",
4102           making a named optional parameter without a default value.  A
4103           nameless optional parameter is permitted to have no default value,
4104           but a named one must have a specific default.  You probably want
4105           "$a = undef".
4106
4107       "our" variable %s redeclared
4108           (W shadow) You seem to have already declared the same global once
4109           before in the current lexical scope.
4110
4111       Out of memory!
4112           (X) The malloc() function returned 0, indicating there was
4113           insufficient remaining memory (or virtual memory) to satisfy the
4114           request.  Perl has no option but to exit immediately.
4115
4116           At least in Unix you may be able to get past this by increasing
4117           your process datasize limits: in csh/tcsh use "limit" and "limit
4118           datasize n" (where "n" is the number of kilobytes) to check the
4119           current limits and change them, and in ksh/bash/zsh use "ulimit -a"
4120           and "ulimit -d n", respectively.
4121
4122       Out of memory during %s extend
4123           (X) An attempt was made to extend an array, a list, or a string
4124           beyond the largest possible memory allocation.
4125
4126       Out of memory during "large" request for %s
4127           (F) The malloc() function returned 0, indicating there was
4128           insufficient remaining memory (or virtual memory) to satisfy the
4129           request.  However, the request was judged large enough (compile-
4130           time default is 64K), so a possibility to shut down by trapping
4131           this error is granted.
4132
4133       Out of memory during request for %s
4134           (X)(F) The malloc() function returned 0, indicating there was
4135           insufficient remaining memory (or virtual memory) to satisfy the
4136           request.
4137
4138           The request was judged to be small, so the possibility to trap it
4139           depends on the way perl was compiled.  By default it is not
4140           trappable.  However, if compiled for this, Perl may use the
4141           contents of $^M as an emergency pool after die()ing with this
4142           message.  In this case the error is trappable once, and the error
4143           message will include the line and file where the failed request
4144           happened.
4145
4146       Out of memory during ridiculously large request
4147           (F) You can't allocate more than 2^31+"small amount" bytes.  This
4148           error is most likely to be caused by a typo in the Perl program.
4149           e.g., $arr[time] instead of $arr[$time].
4150
4151       Out of memory for yacc stack
4152           (F) The yacc parser wanted to grow its stack so it could continue
4153           parsing, but realloc() wouldn't give it more memory, virtual or
4154           otherwise.
4155
4156       '.' outside of string in pack
4157           (F) The argument to a '.' in your template tried to move the
4158           working position to before the start of the packed string being
4159           built.
4160
4161       '@' outside of string in unpack
4162           (F) You had a template that specified an absolute position outside
4163           the string being unpacked.  See "pack" in perlfunc.
4164
4165       '@' outside of string with malformed UTF-8 in unpack
4166           (F) You had a template that specified an absolute position outside
4167           the string being unpacked.  The string being unpacked was also
4168           invalid UTF-8.  See "pack" in perlfunc.
4169
4170       overload arg '%s' is invalid
4171           (W overload) The overload pragma was passed an argument it did not
4172           recognize.  Did you mistype an operator?
4173
4174       Overloaded dereference did not return a reference
4175           (F) An object with an overloaded dereference operator was
4176           dereferenced, but the overloaded operation did not return a
4177           reference.  See overload.
4178
4179       Overloaded qr did not return a REGEXP
4180           (F) An object with a "qr" overload was used as part of a match, but
4181           the overloaded operation didn't return a compiled regexp.  See
4182           overload.
4183
4184       %s package attribute may clash with future reserved word: %s
4185           (W reserved) A lowercase attribute name was used that had a
4186           package-specific handler.  That name might have a meaning to Perl
4187           itself some day, even though it doesn't yet.  Perhaps you should
4188           use a mixed-case attribute name, instead.  See attributes.
4189
4190       pack/unpack repeat count overflow
4191           (F) You can't specify a repeat count so large that it overflows
4192           your signed integers.  See "pack" in perlfunc.
4193
4194       page overflow
4195           (W io) A single call to write() produced more lines than can fit on
4196           a page.  See perlform.
4197
4198       panic: %s
4199           (P) An internal error.
4200
4201       panic: attempt to call %s in %s
4202           (P) One of the file test operators entered a code branch that calls
4203           an ACL related-function, but that function is not available on this
4204           platform.  Earlier checks mean that it should not be possible to
4205           enter this branch on this platform.
4206
4207       panic: child pseudo-process was never scheduled
4208           (P) A child pseudo-process in the ithreads implementation on
4209           Windows was not scheduled within the time period allowed and
4210           therefore was not able to initialize properly.
4211
4212       panic: ck_grep, type=%u
4213           (P) Failed an internal consistency check trying to compile a grep.
4214
4215       panic: corrupt saved stack index %ld
4216           (P) The savestack was requested to restore more localized values
4217           than there are in the savestack.
4218
4219       panic: del_backref
4220           (P) Failed an internal consistency check while trying to reset a
4221           weak reference.
4222
4223       panic: do_subst
4224           (P) The internal pp_subst() routine was called with invalid
4225           operational data.
4226
4227       panic: do_trans_%s
4228           (P) The internal do_trans routines were called with invalid
4229           operational data.
4230
4231       panic: fold_constants JMPENV_PUSH returned %d
4232           (P) While attempting folding constants an exception other than an
4233           "eval" failure was caught.
4234
4235       panic: frexp: %f
4236           (P) The library function frexp() failed, making printf("%f")
4237           impossible.
4238
4239       panic: goto, type=%u, ix=%ld
4240           (P) We popped the context stack to a context with the specified
4241           label, and then discovered it wasn't a context we know how to do a
4242           goto in.
4243
4244       panic: gp_free failed to free glob pointer
4245           (P) The internal routine used to clear a typeglob's entries tried
4246           repeatedly, but each time something re-created entries in the glob.
4247           Most likely the glob contains an object with a reference back to
4248           the glob and a destructor that adds a new object to the glob.
4249
4250       panic: INTERPCASEMOD, %s
4251           (P) The lexer got into a bad state at a case modifier.
4252
4253       panic: INTERPCONCAT, %s
4254           (P) The lexer got into a bad state parsing a string with brackets.
4255
4256       panic: kid popen errno read
4257           (F) A forked child returned an incomprehensible message about its
4258           errno.
4259
4260       panic: last, type=%u
4261           (P) We popped the context stack to a block context, and then
4262           discovered it wasn't a block context.
4263
4264       panic: leave_scope clearsv
4265           (P) A writable lexical variable became read-only somehow within the
4266           scope.
4267
4268       panic: leave_scope inconsistency %u
4269           (P) The savestack probably got out of sync.  At least, there was an
4270           invalid enum on the top of it.
4271
4272       panic: magic_killbackrefs
4273           (P) Failed an internal consistency check while trying to reset all
4274           weak references to an object.
4275
4276       panic: malloc, %s
4277           (P) Something requested a negative number of bytes of malloc.
4278
4279       panic: memory wrap
4280           (P) Something tried to allocate either more memory than possible or
4281           a negative amount.
4282
4283       panic: pad_alloc, %p!=%p
4284           (P) The compiler got confused about which scratch pad it was
4285           allocating and freeing temporaries and lexicals from.
4286
4287       panic: pad_free curpad, %p!=%p
4288           (P) The compiler got confused about which scratch pad it was
4289           allocating and freeing temporaries and lexicals from.
4290
4291       panic: pad_free po
4292           (P) A zero scratch pad offset was detected internally.  An attempt
4293           was made to free a target that had not been allocated to begin
4294           with.
4295
4296       panic: pad_reset curpad, %p!=%p
4297           (P) The compiler got confused about which scratch pad it was
4298           allocating and freeing temporaries and lexicals from.
4299
4300       panic: pad_sv po
4301           (P) A zero scratch pad offset was detected internally.  Most likely
4302           an operator needed a target but that target had not been allocated
4303           for whatever reason.
4304
4305       panic: pad_swipe curpad, %p!=%p
4306           (P) The compiler got confused about which scratch pad it was
4307           allocating and freeing temporaries and lexicals from.
4308
4309       panic: pad_swipe po
4310           (P) An invalid scratch pad offset was detected internally.
4311
4312       panic: pp_iter, type=%u
4313           (P) The foreach iterator got called in a non-loop context frame.
4314
4315       panic: pp_match%s
4316           (P) The internal pp_match() routine was called with invalid
4317           operational data.
4318
4319       panic: realloc, %s
4320           (P) Something requested a negative number of bytes of realloc.
4321
4322       panic: reference miscount on nsv in sv_replace() (%d != 1)
4323           (P) The internal sv_replace() function was handed a new SV with a
4324           reference count other than 1.
4325
4326       panic: restartop in %s
4327           (P) Some internal routine requested a goto (or something like it),
4328           and didn't supply the destination.
4329
4330       panic: return, type=%u
4331           (P) We popped the context stack to a subroutine or eval context,
4332           and then discovered it wasn't a subroutine or eval context.
4333
4334       panic: scan_num, %s
4335           (P) scan_num() got called on something that wasn't a number.
4336
4337       panic: Sequence (?{...}): no code block found in regex m/%s/
4338           (P) While compiling a pattern that has embedded (?{}) or (??{})
4339           code blocks, perl couldn't locate the code block that should have
4340           already been seen and compiled by perl before control passed to the
4341           regex compiler.
4342
4343       panic: strxfrm() gets absurd - a => %u, ab => %u
4344           (P) The interpreter's sanity check of the C function strxfrm()
4345           failed.  In your current locale the returned transformation of the
4346           string "ab" is shorter than that of the string "a", which makes no
4347           sense.
4348
4349       panic: sv_chop %s
4350           (P) The sv_chop() routine was passed a position that is not within
4351           the scalar's string buffer.
4352
4353       panic: sv_insert, midend=%p, bigend=%p
4354           (P) The sv_insert() routine was told to remove more string than
4355           there was string.
4356
4357       panic: top_env
4358           (P) The compiler attempted to do a goto, or something weird like
4359           that.
4360
4361       panic: unimplemented op %s (#%d) called
4362           (P) The compiler is screwed up and attempted to use an op that
4363           isn't permitted at run time.
4364
4365       panic: unknown OA_*: %x
4366           (P) The internal routine that handles arguments to "&CORE::foo()"
4367           subroutine calls was unable to determine what type of arguments
4368           were expected.
4369
4370       panic: utf16_to_utf8: odd bytelen
4371           (P) Something tried to call utf16_to_utf8 with an odd (as opposed
4372           to even) byte length.
4373
4374       panic: utf16_to_utf8_reversed: odd bytelen
4375           (P) Something tried to call utf16_to_utf8_reversed with an odd (as
4376           opposed to even) byte length.
4377
4378       panic: yylex, %s
4379           (P) The lexer got into a bad state while processing a case
4380           modifier.
4381
4382       Parentheses missing around "%s" list
4383           (W parenthesis) You said something like
4384
4385               my $foo, $bar = @_;
4386
4387           when you meant
4388
4389               my ($foo, $bar) = @_;
4390
4391           Remember that "my", "our", "local" and "state" bind tighter than
4392           comma.
4393
4394       Parsing code internal error (%s)
4395           (F) Parsing code supplied by an extension violated the parser's API
4396           in a detectable way.
4397
4398       Pattern subroutine nesting without pos change exceeded limit in regex
4399           (F) You used a pattern that uses too many nested subpattern calls
4400           without consuming any text.  Restructure the pattern so text is
4401           consumed before the nesting limit is exceeded.
4402
4403       "-p" destination: %s
4404           (F) An error occurred during the implicit output invoked by the
4405           "-p" command-line switch.  (This output goes to STDOUT unless
4406           you've redirected it with select().)
4407
4408       Perl API version %s of %s does not match %s
4409           (F) The XS module in question was compiled against a different
4410           incompatible version of Perl than the one that has loaded the XS
4411           module.
4412
4413       Perl folding rules are not up-to-date for 0x%X; please use the perlbug
4414       utility to report; in regex; marked by <-- HERE in m/%s/
4415           (S regexp) You used a regular expression with case-insensitive
4416           matching, and there is a bug in Perl in which the built-in regular
4417           expression folding rules are not accurate.  This may lead to
4418           incorrect results.  Please report this as a bug to
4419           <https://github.com/Perl/perl5/issues>.
4420
4421       PerlIO layer ':win32' is experimental
4422           (S experimental::win32_perlio) The ":win32" PerlIO layer is
4423           experimental.  If you want to take the risk of using this layer,
4424           simply disable this warning:
4425
4426               no warnings "experimental::win32_perlio";
4427
4428       Perl_my_%s() not available
4429           (F) Your platform has very uncommon byte-order and integer size, so
4430           it was not possible to set up some or all fixed-width byte-order
4431           conversion functions.  This is only a problem when you're using the
4432           '<' or '>' modifiers in (un)pack templates.  See "pack" in
4433           perlfunc.
4434
4435       Perl %s required (did you mean %s?)--this is only %s, stopped
4436           (F) The code you are trying to run has asked for a newer version of
4437           Perl than you are running.  Perhaps "use 5.10" was written instead
4438           of "use 5.010" or "use v5.10".  Without the leading "v", the number
4439           is interpreted as a decimal, with every three digits after the
4440           decimal point representing a part of the version number.  So 5.10
4441           is equivalent to v5.100.
4442
4443       Perl %s required--this is only %s, stopped
4444           (F) The module in question uses features of a version of Perl more
4445           recent than the currently running version.  How long has it been
4446           since you upgraded, anyway?  See "require" in perlfunc.
4447
4448       PERL_SH_DIR too long
4449           (F) An error peculiar to OS/2.  PERL_SH_DIR is the directory to
4450           find the "sh"-shell in.  See "PERL_SH_DIR" in perlos2.
4451
4452       PERL_SIGNALS illegal: "%s"
4453           (X) See "PERL_SIGNALS" in perlrun for legal values.
4454
4455       Perls since %s too modern--this is %s, stopped
4456           (F) The code you are trying to run claims it will not run on the
4457           version of Perl you are using because it is too new.  Maybe the
4458           code needs to be updated, or maybe it is simply wrong and the
4459           version check should just be removed.
4460
4461       perl: warning: Non hex character in '$ENV{PERL_HASH_SEED}', seed only
4462       partially set
4463           (S) PERL_HASH_SEED should match /^\s*(?:0x)?[0-9a-fA-F]+\s*\z/ but
4464           it contained a non hex character.  This could mean you are not
4465           using the hash seed you think you are.
4466
4467       perl: warning: Setting locale failed.
4468           (S) The whole warning message will look something like:
4469
4470                   perl: warning: Setting locale failed.
4471                   perl: warning: Please check that your locale settings:
4472                           LC_ALL = "En_US",
4473                           LANG = (unset)
4474                       are supported and installed on your system.
4475                   perl: warning: Falling back to the standard locale ("C").
4476
4477           Exactly what were the failed locale settings varies.  In the above
4478           the settings were that the LC_ALL was "En_US" and the LANG had no
4479           value.  This error means that Perl detected that you and/or your
4480           operating system supplier and/or system administrator have set up
4481           the so-called locale system but Perl could not use those settings.
4482           This was not dead serious, fortunately: there is a "default locale"
4483           called "C" that Perl can and will use, and the script will be run.
4484           Before you really fix the problem, however, you will get the same
4485           error message each time you run Perl.  How to really fix the
4486           problem can be found in perllocale section LOCALE PROBLEMS.
4487
4488       perl: warning: strange setting in '$ENV{PERL_PERTURB_KEYS}': '%s'
4489           (S) Perl was run with the environment variable PERL_PERTURB_KEYS
4490           defined but containing an unexpected value.  The legal values of
4491           this setting are as follows.
4492
4493             Numeric | String        | Result
4494             --------+---------------+-----------------------------------------
4495             0       | NO            | Disables key traversal randomization
4496             1       | RANDOM        | Enables full key traversal randomization
4497             2       | DETERMINISTIC | Enables repeatable key traversal
4498                     |               | randomization
4499
4500           Both numeric and string values are accepted, but note that string
4501           values are case sensitive.  The default for this setting is
4502           "RANDOM" or 1.
4503
4504       pid %x not a child
4505           (W exec) A warning peculiar to VMS.  Waitpid() was asked to wait
4506           for a process which isn't a subprocess of the current process.
4507           While this is fine from VMS' perspective, it's probably not what
4508           you intended.
4509
4510       'P' must have an explicit size in unpack
4511           (F) The unpack format P must have an explicit size, not "*".
4512
4513       POSIX class [:%s:] unknown in regex; marked by <-- HERE in m/%s/
4514           (F) The class in the character class [: :] syntax is unknown.  The
4515           <-- HERE shows whereabouts in the regular expression the problem
4516           was discovered.  Note that the POSIX character classes do not have
4517           the "is" prefix the corresponding C interfaces have: in other
4518           words, it's "[[:print:]]", not "isprint".  See perlre.
4519
4520       POSIX getpgrp can't take an argument
4521           (F) Your system has POSIX getpgrp(), which takes no argument,
4522           unlike the BSD version, which takes a pid.
4523
4524       POSIX syntax [%c %c] belongs inside character classes%s in regex;
4525       marked by <-- HERE in m/%s/
4526           (W regexp) Perl thinks that you intended to write a POSIX character
4527           class, but didn't use enough brackets.  These POSIX class
4528           constructs [: :], [= =], and [. .]  go inside character classes,
4529           the [] are part of the construct, for example:
4530           "qr/[012[:alpha:]345]/".  What the regular expression pattern
4531           compiled to is probably not what you were intending.  For example,
4532           "qr/[:alpha:]/" compiles to a regular bracketed character class
4533           consisting of the four characters ":",  "a",  "l", "h", and "p".
4534           To specify the POSIX class, it should have been written
4535           "qr/[[:alpha:]]/".
4536
4537           Note that [= =] and [. .] are not currently implemented; they are
4538           simply placeholders for future extensions and will cause fatal
4539           errors.  The <-- HERE shows whereabouts in the regular expression
4540           the problem was discovered.  See perlre.
4541
4542           If the specification of the class was not completely valid, the
4543           message indicates that.
4544
4545       POSIX syntax [. .] is reserved for future extensions in regex; marked
4546       by <-- HERE in m/%s/
4547           (F) Within regular expression character classes ([]) the syntax
4548           beginning with "[." and ending with ".]" is reserved for future
4549           extensions.  If you need to represent those character sequences
4550           inside a regular expression character class, just quote the square
4551           brackets with the backslash: "\[."  and ".\]".  The <-- HERE shows
4552           whereabouts in the regular expression the problem was discovered.
4553           See perlre.
4554
4555       POSIX syntax [= =] is reserved for future extensions in regex; marked
4556       by <-- HERE in m/%s/
4557           (F) Within regular expression character classes ([]) the syntax
4558           beginning with "[=" and ending with "=]" is reserved for future
4559           extensions.  If you need to represent those character sequences
4560           inside a regular expression character class, just quote the square
4561           brackets with the backslash: "\[=" and "=\]".  The <-- HERE shows
4562           whereabouts in the regular expression the problem was discovered.
4563           See perlre.
4564
4565       Possible attempt to put comments in qw() list
4566           (W qw) qw() lists contain items separated by whitespace; as with
4567           literal strings, comment characters are not ignored, but are
4568           instead treated as literal data.  (You may have used different
4569           delimiters than the parentheses shown here; braces are also
4570           frequently used.)
4571
4572           You probably wrote something like this:
4573
4574               @list = qw(
4575                   a # a comment
4576                   b # another comment
4577               );
4578
4579           when you should have written this:
4580
4581               @list = qw(
4582                   a
4583                   b
4584               );
4585
4586           If you really want comments, build your list the old-fashioned way,
4587           with quotes and commas:
4588
4589               @list = (
4590                   'a',    # a comment
4591                   'b',    # another comment
4592               );
4593
4594       Possible attempt to separate words with commas
4595           (W qw) qw() lists contain items separated by whitespace; therefore
4596           commas aren't needed to separate the items.  (You may have used
4597           different delimiters than the parentheses shown here; braces are
4598           also frequently used.)
4599
4600           You probably wrote something like this:
4601
4602               qw! a, b, c !;
4603
4604           which puts literal commas into some of the list items.  Write it
4605           without commas if you don't want them to appear in your data:
4606
4607               qw! a b c !;
4608
4609       Possible memory corruption: %s overflowed 3rd argument
4610           (F) An ioctl() or fcntl() returned more than Perl was bargaining
4611           for.  Perl guesses a reasonable buffer size, but puts a sentinel
4612           byte at the end of the buffer just in case.  This sentinel byte got
4613           clobbered, and Perl assumes that memory is now corrupted.  See
4614           "ioctl" in perlfunc.
4615
4616       Possible precedence issue with control flow operator
4617           (W syntax) There is a possible problem with the mixing of a control
4618           flow operator (e.g. "return") and a low-precedence operator like
4619           "or".  Consider:
4620
4621               sub { return $a or $b; }
4622
4623           This is parsed as:
4624
4625               sub { (return $a) or $b; }
4626
4627           Which is effectively just:
4628
4629               sub { return $a; }
4630
4631           Either use parentheses or the high-precedence variant of the
4632           operator.
4633
4634           Note this may be also triggered for constructs like:
4635
4636               sub { 1 if die; }
4637
4638       Possible precedence problem on bitwise %s operator
4639           (W precedence) Your program uses a bitwise logical operator in
4640           conjunction with a numeric comparison operator, like this :
4641
4642               if ($x & $y == 0) { ... }
4643
4644           This expression is actually equivalent to "$x & ($y == 0)", due to
4645           the higher precedence of "==".  This is probably not what you want.
4646           (If you really meant to write this, disable the warning, or,
4647           better, put the parentheses explicitly and write "$x & ($y == 0)").
4648
4649       Possible unintended interpolation of $\ in regex
4650           (W ambiguous) You said something like "m/$\/" in a regex.  The
4651           regex "m/foo$\s+bar/m" translates to: match the word 'foo', the
4652           output record separator (see "$\" in perlvar) and the letter 's'
4653           (one time or more) followed by the word 'bar'.
4654
4655           If this is what you intended then you can silence the warning by
4656           using "m/${\}/" (for example: "m/foo${\}s+bar/").
4657
4658           If instead you intended to match the word 'foo' at the end of the
4659           line followed by whitespace and the word 'bar' on the next line
4660           then you can use "m/$(?)\/" (for example: "m/foo$(?)\s+bar/").
4661
4662       Possible unintended interpolation of %s in string
4663           (W ambiguous) You said something like '@foo' in a double-quoted
4664           string but there was no array @foo in scope at the time.  If you
4665           wanted a literal @foo, then write it as \@foo; otherwise find out
4666           what happened to the array you apparently lost track of.
4667
4668       Precedence problem: open %s should be open(%s)
4669           (S precedence) The old irregular construct
4670
4671               open FOO || die;
4672
4673           is now misinterpreted as
4674
4675               open(FOO || die);
4676
4677           because of the strict regularization of Perl 5's grammar into unary
4678           and list operators.  (The old open was a little of both.)  You must
4679           put parentheses around the filehandle, or use the new "or" operator
4680           instead of "||".
4681
4682       Premature end of script headers
4683           See "500 Server error".
4684
4685       printf() on closed filehandle %s
4686           (W closed) The filehandle you're writing to got itself closed
4687           sometime before now.  Check your control flow.
4688
4689       print() on closed filehandle %s
4690           (W closed) The filehandle you're printing on got itself closed
4691           sometime before now.  Check your control flow.
4692
4693       Process terminated by SIG%s
4694           (W) This is a standard message issued by OS/2 applications, while
4695           *nix applications die in silence.  It is considered a feature of
4696           the OS/2 port.  One can easily disable this by appropriate
4697           sighandlers, see "Signals" in perlipc.  See also "Process
4698           terminated by SIGTERM/SIGINT" in perlos2.
4699
4700       Prototype after '%c' for %s : %s
4701           (W illegalproto) A character follows % or @ in a prototype.  This
4702           is useless, since % and @ gobble the rest of the subroutine
4703           arguments.
4704
4705       Prototype mismatch: %s vs %s
4706           (S prototype) The subroutine being declared or defined had
4707           previously been declared or defined with a different function
4708           prototype.
4709
4710       Prototype not terminated
4711           (F) You've omitted the closing parenthesis in a function prototype
4712           definition.
4713
4714       Prototype '%s' overridden by attribute 'prototype(%s)' in %s
4715           (W prototype) A prototype was declared in both the parentheses
4716           after the sub name and via the prototype attribute.  The prototype
4717           in parentheses is useless, since it will be replaced by the
4718           prototype from the attribute before it's ever used.
4719
4720       Quantifier follows nothing in regex; marked by <-- HERE in m/%s/
4721           (F) You started a regular expression with a quantifier.  Backslash
4722           it if you meant it literally.  The <-- HERE shows whereabouts in
4723           the regular expression the problem was discovered.  See perlre.
4724
4725       Quantifier in {,} bigger than %d in regex; marked by <-- HERE in m/%s/
4726           (F) There is currently a limit to the size of the min and max
4727           values of the {min,max} construct.  The <-- HERE shows whereabouts
4728           in the regular expression the problem was discovered.  See perlre.
4729
4730       Quantifier {n,m} with n > m can't match in regex
4731       Quantifier {n,m} with n > m can't match in regex; marked by <-- HERE in
4732       m/%s/
4733           (W regexp) Minima should be less than or equal to maxima.  If you
4734           really want your regexp to match something 0 times, just put {0}.
4735
4736       Quantifier unexpected on zero-length expression in regex m/%s/
4737           (W regexp) You applied a regular expression quantifier in a place
4738           where it makes no sense, such as on a zero-width assertion.  Try
4739           putting the quantifier inside the assertion instead.  For example,
4740           the way to match "abc" provided that it is followed by three
4741           repetitions of "xyz" is "/abc(?=(?:xyz){3})/", not
4742           "/abc(?=xyz){3}/".
4743
4744       Range iterator outside integer range
4745           (F) One (or both) of the numeric arguments to the range operator
4746           ".."  are outside the range which can be represented by integers
4747           internally.  One possible workaround is to force Perl to use
4748           magical string increment by prepending "0" to your numbers.
4749
4750       Ranges of ASCII printables should be some subset of "0-9", "A-Z", or
4751       "a-z" in regex; marked by <-- HERE in m/%s/
4752           (W regexp) (only under "use re 'strict'" or within "(?[...])")
4753
4754           Stricter rules help to find typos and other errors.  Perhaps you
4755           didn't even intend a range here, if the "-" was meant to be some
4756           other character, or should have been escaped (like "\-").  If you
4757           did intend a range, the one that was used is not portable between
4758           ASCII and EBCDIC platforms, and doesn't have an obvious meaning to
4759           a casual reader.
4760
4761            [3-7]    # OK; Obvious and portable
4762            [d-g]    # OK; Obvious and portable
4763            [A-Y]    # OK; Obvious and portable
4764            [A-z]    # WRONG; Not portable; not clear what is meant
4765            [a-Z]    # WRONG; Not portable; not clear what is meant
4766            [%-.]    # WRONG; Not portable; not clear what is meant
4767            [\x41-Z] # WRONG; Not portable; not obvious to non-geek
4768
4769           (You can force portability by specifying a Unicode range, which
4770           means that the endpoints are specified by "\N{...}", but the
4771           meaning may still not be obvious.)  The stricter rules require that
4772           ranges that start or stop with an ASCII character that is not a
4773           control have all their endpoints be the literal character, and not
4774           some escape sequence (like "\x41"), and the ranges must be all
4775           digits, or all uppercase letters, or all lowercase letters.
4776
4777       Ranges of digits should be from the same group in regex; marked by
4778       <-- HERE in m/%s/
4779           (W regexp) (only under "use re 'strict'" or within "(?[...])")
4780
4781           Stricter rules help to find typos and other errors.  You included a
4782           range, and at least one of the end points is a decimal digit.
4783           Under the stricter rules, when this happens, both end points should
4784           be digits in the same group of 10 consecutive digits.
4785
4786       readdir() attempted on invalid dirhandle %s
4787           (W io) The dirhandle you're reading from is either closed or not
4788           really a dirhandle.  Check your control flow.
4789
4790       readline() on closed filehandle %s
4791           (W closed) The filehandle you're reading from got itself closed
4792           sometime before now.  Check your control flow.
4793
4794       readline() on unopened filehandle %s
4795           (W unopened) The filehandle you're reading from was never opened.
4796           Check your control flow.
4797
4798       read() on closed filehandle %s
4799           (W closed) You tried to read from a closed filehandle.
4800
4801       read() on unopened filehandle %s
4802           (W unopened) You tried to read from a filehandle that was never
4803           opened.
4804
4805       Reallocation too large: %x
4806           (F) You can't allocate more than 64K on an MS-DOS machine.
4807
4808       realloc() of freed memory ignored
4809           (S malloc) An internal routine called realloc() on something that
4810           had already been freed.
4811
4812       Recompile perl with -DDEBUGGING to use -D switch
4813           (S debugging) You can't use the -D option unless the code to
4814           produce the desired output is compiled into Perl, which entails
4815           some overhead, which is why it's currently left out of your copy.
4816
4817       Recursive call to Perl_load_module in PerlIO_find_layer
4818           (P) It is currently not permitted to load modules when creating a
4819           filehandle inside an %INC hook.  This can happen with "open my $fh,
4820           '<', \$scalar", which implicitly loads PerlIO::scalar.  Try loading
4821           PerlIO::scalar explicitly first.
4822
4823       Recursive inheritance detected in package '%s'
4824           (F) While calculating the method resolution order (MRO) of a
4825           package, Perl believes it found an infinite loop in the @ISA
4826           hierarchy.  This is a crude check that bails out after 100 levels
4827           of @ISA depth.
4828
4829       Redundant argument in %s
4830           (W redundant) You called a function with more arguments than other
4831           arguments you supplied indicated would be needed.  Currently only
4832           emitted when a printf-type format required fewer arguments than
4833           were supplied, but might be used in the future for e.g. "pack" in
4834           perlfunc.
4835
4836       refcnt_dec: fd %d%s
4837       refcnt: fd %d%s
4838       refcnt_inc: fd %d%s
4839           (P) Perl's I/O implementation failed an internal consistency check.
4840           If you see this message, something is very wrong.
4841
4842       Reference found where even-sized list expected
4843           (W misc) You gave a single reference where Perl was expecting a
4844           list with an even number of elements (for assignment to a hash).
4845           This usually means that you used the anon hash constructor when you
4846           meant to use parens.  In any case, a hash requires key/value pairs.
4847
4848               %hash = { one => 1, two => 2, };    # WRONG
4849               %hash = [ qw/ an anon array / ];    # WRONG
4850               %hash = ( one => 1, two => 2, );    # right
4851               %hash = qw( one 1 two 2 );                  # also fine
4852
4853       Reference is already weak
4854           (W misc) You have attempted to weaken a reference that is already
4855           weak.  Doing so has no effect.
4856
4857       Reference is not weak
4858           (W misc) You have attempted to unweaken a reference that is not
4859           weak.  Doing so has no effect.
4860
4861       Reference to invalid group 0 in regex; marked by <-- HERE in m/%s/
4862           (F) You used "\g0" or similar in a regular expression.  You may
4863           refer to capturing parentheses only with strictly positive integers
4864           (normal backreferences) or with strictly negative integers
4865           (relative backreferences).  Using 0 does not make sense.
4866
4867       Reference to nonexistent group in regex; marked by <-- HERE in m/%s/
4868           (F) You used something like "\7" in your regular expression, but
4869           there are not at least seven sets of capturing parentheses in the
4870           expression.  If you wanted to have the character with ordinal 7
4871           inserted into the regular expression, prepend zeroes to make it
4872           three digits long: "\007"
4873
4874           The <-- HERE shows whereabouts in the regular expression the
4875           problem was discovered.
4876
4877       Reference to nonexistent named group in regex; marked by <-- HERE in
4878       m/%s/
4879           (F) You used something like "\k'NAME'" or "\k<NAME>" in your
4880           regular expression, but there is no corresponding named capturing
4881           parentheses such as "(?'NAME'...)" or "(?<NAME>...)".  Check if the
4882           name has been spelled correctly both in the backreference and the
4883           declaration.
4884
4885           The <-- HERE shows whereabouts in the regular expression the
4886           problem was discovered.
4887
4888       Reference to nonexistent or unclosed group in regex; marked by <-- HERE
4889       in m/%s/
4890           (F) You used something like "\g{-7}" in your regular expression,
4891           but there are not at least seven sets of closed capturing
4892           parentheses in the expression before where the "\g{-7}" was
4893           located.
4894
4895           The <-- HERE shows whereabouts in the regular expression the
4896           problem was discovered.
4897
4898       regexp memory corruption
4899           (P) The regular expression engine got confused by what the regular
4900           expression compiler gave it.
4901
4902       Regexp modifier "/%c" may appear a maximum of twice
4903       Regexp modifier "%c" may appear a maximum of twice in regex; marked by
4904       <-- HERE in m/%s/
4905           (F) The regular expression pattern had too many occurrences of the
4906           specified modifier.  Remove the extraneous ones.
4907
4908       Regexp modifier "%c" may not appear after the "-" in regex; marked by
4909       <-- HERE in m/%s/
4910           (F) Turning off the given modifier has the side effect of turning
4911           on another one.  Perl currently doesn't allow this.  Reword the
4912           regular expression to use the modifier you want to turn on (and
4913           place it before the minus), instead of the one you want to turn
4914           off.
4915
4916       Regexp modifier "/%c" may not appear twice
4917       Regexp modifier "%c" may not appear twice in regex; marked by <-- HERE
4918       in m/%s/
4919           (F) The regular expression pattern had too many occurrences of the
4920           specified modifier.  Remove the extraneous ones.
4921
4922       Regexp modifiers "/%c" and "/%c" are mutually exclusive
4923       Regexp modifiers "%c" and "%c" are mutually exclusive in regex; marked
4924       by <-- HERE in m/%s/
4925           (F) The regular expression pattern had more than one of these
4926           mutually exclusive modifiers.  Retain only the modifier that is
4927           supposed to be there.
4928
4929       Regexp out of space in regex m/%s/
4930           (P) A "can't happen" error, because safemalloc() should have caught
4931           it earlier.
4932
4933       Repeated format line will never terminate (~~ and @#)
4934           (F) Your format contains the ~~ repeat-until-blank sequence and a
4935           numeric field that will never go blank so that the repetition never
4936           terminates.  You might use ^# instead.  See perlform.
4937
4938       Replacement list is longer than search list
4939           (W misc) You have used a replacement list that is longer than the
4940           search list.  So the additional elements in the replacement list
4941           are meaningless.
4942
4943       '(*%s' requires a terminating ':' in regex; marked by <-- HERE in m/%s/
4944           (F) You used a construct that needs a colon and pattern argument.
4945           Supply these or check that you are using the right construct.
4946
4947       '%s' resolved to '\o{%s}%d'
4948           As of Perl 5.32, this message is no longer generated.  Instead, see
4949           "Non-octal character '%c' terminates \o early.  Resolved as "%s"".
4950           (W misc, regexp)  You wrote something like "\08", or "\179" in a
4951           double-quotish string.  All but the last digit is treated as a
4952           single character, specified in octal.  The last digit is the next
4953           character in the string.  To tell Perl that this is indeed what you
4954           want, you can use the "\o{ }" syntax, or use exactly three digits
4955           to specify the octal for the character.
4956
4957       Reversed %s= operator
4958           (W syntax) You wrote your assignment operator backwards.  The =
4959           must always come last, to avoid ambiguity with subsequent unary
4960           operators.
4961
4962       rewinddir() attempted on invalid dirhandle %s
4963           (W io) The dirhandle you tried to do a rewinddir() on is either
4964           closed or not really a dirhandle.  Check your control flow.
4965
4966       Scalars leaked: %d
4967           (S internal) Something went wrong in Perl's internal bookkeeping of
4968           scalars: not all scalar variables were deallocated by the time Perl
4969           exited.  What this usually indicates is a memory leak, which is of
4970           course bad, especially if the Perl program is intended to be long-
4971           running.
4972
4973       Scalar value @%s[%s] better written as $%s[%s]
4974           (W syntax) You've used an array slice (indicated by @) to select a
4975           single element of an array.  Generally it's better to ask for a
4976           scalar value (indicated by $).  The difference is that $foo[&bar]
4977           always behaves like a scalar, both when assigning to it and when
4978           evaluating its argument, while @foo[&bar] behaves like a list when
4979           you assign to it, and provides a list context to its subscript,
4980           which can do weird things if you're expecting only one subscript.
4981
4982           On the other hand, if you were actually hoping to treat the array
4983           element as a list, you need to look into how references work,
4984           because Perl will not magically convert between scalars and lists
4985           for you.  See perlref.
4986
4987       Scalar value @%s{%s} better written as $%s{%s}
4988           (W syntax) You've used a hash slice (indicated by @) to select a
4989           single element of a hash.  Generally it's better to ask for a
4990           scalar value (indicated by $).  The difference is that $foo{&bar}
4991           always behaves like a scalar, both when assigning to it and when
4992           evaluating its argument, while @foo{&bar} behaves like a list when
4993           you assign to it, and provides a list context to its subscript,
4994           which can do weird things if you're expecting only one subscript.
4995
4996           On the other hand, if you were actually hoping to treat the hash
4997           element as a list, you need to look into how references work,
4998           because Perl will not magically convert between scalars and lists
4999           for you.  See perlref.
5000
5001       Search pattern not terminated
5002           (F) The lexer couldn't find the final delimiter of a // or m{}
5003           construct.  Remember that bracketing delimiters count nesting
5004           level.  Missing the leading "$" from a variable $m may cause this
5005           error.
5006
5007           Note that since Perl 5.10.0 a // can also be the defined-or
5008           construct, not just the empty search pattern.  Therefore code
5009           written in Perl 5.10.0 or later that uses the // as the defined-or
5010           can be misparsed by pre-5.10.0 Perls as a non-terminated search
5011           pattern.
5012
5013       seekdir() attempted on invalid dirhandle %s
5014           (W io) The dirhandle you are doing a seekdir() on is either closed
5015           or not really a dirhandle.  Check your control flow.
5016
5017       %sseek() on unopened filehandle
5018           (W unopened) You tried to use the seek() or sysseek() function on a
5019           filehandle that was either never opened or has since been closed.
5020
5021       select not implemented
5022           (F) This machine doesn't implement the select() system call.
5023
5024       Self-ties of arrays and hashes are not supported
5025           (F) Self-ties are of arrays and hashes are not supported in the
5026           current implementation.
5027
5028       Semicolon seems to be missing
5029           (W semicolon) A nearby syntax error was probably caused by a
5030           missing semicolon, or possibly some other missing operator, such as
5031           a comma.
5032
5033       semi-panic: attempt to dup freed string
5034           (S internal) The internal newSVsv() routine was called to duplicate
5035           a scalar that had previously been marked as free.
5036
5037       sem%s not implemented
5038           (F) You don't have System V semaphore IPC on your system.
5039
5040       send() on closed socket %s
5041           (W closed) The socket you're sending to got itself closed sometime
5042           before now.  Check your control flow.
5043
5044       Sequence "\c{" invalid
5045           (F) These three characters may not appear in sequence in a double-
5046           quotish context.  This message is raised only on non-ASCII
5047           platforms (a different error message is output on ASCII ones).  If
5048           you were intending to specify a control character with this
5049           sequence, you'll have to use a different way to specify it.
5050
5051       Sequence (? incomplete in regex; marked by <-- HERE in m/%s/
5052           (F) A regular expression ended with an incomplete extension (?.
5053           The <-- HERE shows whereabouts in the regular expression the
5054           problem was discovered.  See perlre.
5055
5056       Sequence (?%c...) not implemented in regex; marked by <-- HERE in m/%s/
5057           (F) A proposed regular expression extension has the character
5058           reserved but has not yet been written.  The <-- HERE shows
5059           whereabouts in the regular expression the problem was discovered.
5060           See perlre.
5061
5062       Sequence (?%s...) not recognized in regex; marked by <-- HERE in m/%s/
5063           (F) You used a regular expression extension that doesn't make
5064           sense.  The <-- HERE shows whereabouts in the regular expression
5065           the problem was discovered.  This may happen when using the
5066           "(?^...)" construct to tell Perl to use the default regular
5067           expression modifiers, and you redundantly specify a default
5068           modifier.  For other causes, see perlre.
5069
5070       Sequence (?#... not terminated in regex m/%s/
5071           (F) A regular expression comment must be terminated by a closing
5072           parenthesis.  Embedded parentheses aren't allowed.  See perlre.
5073
5074       Sequence (?&... not terminated in regex; marked by <-- HERE in m/%s/
5075           (F) A named reference of the form "(?&...)" was missing the final
5076           closing parenthesis after the name.  The <-- HERE shows whereabouts
5077           in the regular expression the problem was discovered.
5078
5079       Sequence (?%c... not terminated in regex; marked by <-- HERE in m/%s/
5080           (F) A named group of the form "(?'...')" or "(?<...>)" was missing
5081           the final closing quote or angle bracket.  The <-- HERE shows
5082           whereabouts in the regular expression the problem was discovered.
5083
5084       Sequence (?(%c... not terminated in regex; marked by <-- HERE in m/%s/
5085           (F) A named reference of the form "(?('...')...)" or
5086           "(?(<...>)...)" was missing the final closing quote or angle
5087           bracket after the name.  The <-- HERE shows whereabouts in the
5088           regular expression the problem was discovered.
5089
5090       Sequence (?... not terminated in regex; marked by <-- HERE in m/%s/
5091           (F) There was no matching closing parenthesis for the '('.  The
5092           <-- HERE shows whereabouts in the regular expression the problem
5093           was discovered.
5094
5095       Sequence \%s... not terminated in regex; marked by <-- HERE in m/%s/
5096           (F) The regular expression expects a mandatory argument following
5097           the escape sequence and this has been omitted or incorrectly
5098           written.
5099
5100       Sequence (?{...}) not terminated with ')'
5101           (F) The end of the perl code contained within the {...} must be
5102           followed immediately by a ')'.
5103
5104       Sequence (?P>... not terminated in regex; marked by <-- HERE in m/%s/
5105           (F) A named reference of the form "(?P>...)" was missing the final
5106           closing parenthesis after the name.  The <-- HERE shows whereabouts
5107           in the regular expression the problem was discovered.
5108
5109       Sequence (?P<... not terminated in regex; marked by <-- HERE in m/%s/
5110           (F) A named group of the form "(?P<...>')" was missing the final
5111           closing angle bracket.  The <-- HERE shows whereabouts in the
5112           regular expression the problem was discovered.
5113
5114       Sequence ?P=... not terminated in regex; marked by <-- HERE in m/%s/
5115           (F) A named reference of the form "(?P=...)" was missing the final
5116           closing parenthesis after the name.  The <-- HERE shows whereabouts
5117           in the regular expression the problem was discovered.
5118
5119       Sequence (?R) not terminated in regex m/%s/
5120           (F) An "(?R)" or "(?0)" sequence in a regular expression was
5121           missing the final parenthesis.
5122
5123       500 Server error
5124           (A) This is the error message generally seen in a browser window
5125           when trying to run a CGI program (including SSI) over the web.  The
5126           actual error text varies widely from server to server.  The most
5127           frequently-seen variants are "500 Server error", "Method
5128           (something) not permitted", "Document contains no data", "Premature
5129           end of script headers", and "Did not produce a valid header".
5130
5131           This is a CGI error, not a Perl error.
5132
5133           You need to make sure your script is executable, is accessible by
5134           the user CGI is running the script under (which is probably not the
5135           user account you tested it under), does not rely on any environment
5136           variables (like PATH) from the user it isn't running under, and
5137           isn't in a location where the CGI server can't find it, basically,
5138           more or less.  Please see the following for more information:
5139
5140                   https://www.perl.org/CGI_MetaFAQ.html
5141                   http://www.htmlhelp.org/faq/cgifaq.html
5142                   http://www.w3.org/Security/Faq/
5143
5144           You should also look at perlfaq9.
5145
5146       setegid() not implemented
5147           (F) You tried to assign to $), and your operating system doesn't
5148           support the setegid() system call (or equivalent), or at least
5149           Configure didn't think so.
5150
5151       seteuid() not implemented
5152           (F) You tried to assign to $>, and your operating system doesn't
5153           support the seteuid() system call (or equivalent), or at least
5154           Configure didn't think so.
5155
5156       setpgrp can't take arguments
5157           (F) Your system has the setpgrp() from BSD 4.2, which takes no
5158           arguments, unlike POSIX setpgid(), which takes a process ID and
5159           process group ID.
5160
5161       setrgid() not implemented
5162           (F) You tried to assign to $(, and your operating system doesn't
5163           support the setrgid() system call (or equivalent), or at least
5164           Configure didn't think so.
5165
5166       setruid() not implemented
5167           (F) You tried to assign to $<, and your operating system doesn't
5168           support the setruid() system call (or equivalent), or at least
5169           Configure didn't think so.
5170
5171       setsockopt() on closed socket %s
5172           (W closed) You tried to set a socket option on a closed socket.
5173           Did you forget to check the return value of your socket() call?
5174           See "setsockopt" in perlfunc.
5175
5176       Setting $/ to a reference to %s is forbidden
5177           (F) You assigned a reference to a scalar to $/ where the referenced
5178           item is not a positive integer.  In older perls this appeared to
5179           work the same as setting it to "undef" but was in fact internally
5180           different, less efficient and with very bad luck could have
5181           resulted in your file being split by a stringified form of the
5182           reference.
5183
5184           In Perl 5.20.0 this was changed so that it would be exactly the
5185           same as setting $/ to undef, with the exception that this warning
5186           would be thrown.
5187
5188           You are recommended to change your code to set $/ to "undef"
5189           explicitly if you wish to slurp the file.  As of Perl 5.28
5190           assigning $/ to a reference to an integer which isn't positive is a
5191           fatal error.
5192
5193       Setting $/ to %s reference is forbidden
5194           (F) You tried to assign a reference to a non integer to $/.  In
5195           older Perls this would have behaved similarly to setting it to a
5196           reference to a positive integer, where the integer was the address
5197           of the reference.  As of Perl 5.20.0 this is a fatal error, to
5198           allow future versions of Perl to use non-integer refs for more
5199           interesting purposes.
5200
5201       shm%s not implemented
5202           (F) You don't have System V shared memory IPC on your system.
5203
5204       !=~ should be !~
5205           (W syntax) The non-matching operator is !~, not !=~.  !=~ will be
5206           interpreted as the != (numeric not equal) and ~ (1's complement)
5207           operators: probably not what you intended.
5208
5209       /%s/ should probably be written as "%s"
5210           (W syntax) You have used a pattern where Perl expected to find a
5211           string, as in the first argument to "join".  Perl will treat the
5212           true or false result of matching the pattern against $_ as the
5213           string, which is probably not what you had in mind.
5214
5215       shutdown() on closed socket %s
5216           (W closed) You tried to do a shutdown on a closed socket.  Seems a
5217           bit superfluous.
5218
5219       SIG%s handler "%s" not defined
5220           (W signal) The signal handler named in %SIG doesn't, in fact,
5221           exist.  Perhaps you put it into the wrong package?
5222
5223       Slab leaked from cv %p
5224           (S) If you see this message, then something is seriously wrong with
5225           the internal bookkeeping of op trees.  An op tree needed to be
5226           freed after a compilation error, but could not be found, so it was
5227           leaked instead.
5228
5229       sleep(%u) too large
5230           (W overflow) You called "sleep" with a number that was larger than
5231           it can reliably handle and "sleep" probably slept for less time
5232           than requested.
5233
5234       Slurpy parameter not last
5235           (F) In a subroutine signature, you put something after a slurpy
5236           (array or hash) parameter.  The slurpy parameter takes all the
5237           available arguments, so there can't be any left to fill later
5238           parameters.
5239
5240       Smart matching a non-overloaded object breaks encapsulation
5241           (F) You should not use the "~~" operator on an object that does not
5242           overload it: Perl refuses to use the object's underlying structure
5243           for the smart match.
5244
5245       Smartmatch is experimental
5246           (S experimental::smartmatch) This warning is emitted if you use the
5247           smartmatch ("~~") operator.  This is currently an experimental
5248           feature, and its details are subject to change in future releases
5249           of Perl.  Particularly, its current behavior is noticed for being
5250           unnecessarily complex and unintuitive, and is very likely to be
5251           overhauled.
5252
5253       Sorry, hash keys must be smaller than 2**31 bytes
5254           (F) You tried to create a hash containing a very large key, where
5255           "very large" means that it needs at least 2 gigabytes to store.
5256           Unfortunately, Perl doesn't yet handle such large hash keys. You
5257           should reconsider your design to avoid hashing such a long string
5258           directly.
5259
5260       sort is now a reserved word
5261           (F) An ancient error message that almost nobody ever runs into
5262           anymore.  But before sort was a keyword, people sometimes used it
5263           as a filehandle.
5264
5265       Source filters apply only to byte streams
5266           (F) You tried to activate a source filter (usually by loading a
5267           source filter module) within a string passed to "eval".  This is
5268           not permitted under the "unicode_eval" feature.  Consider using
5269           "evalbytes" instead.  See feature.
5270
5271       splice() offset past end of array
5272           (W misc) You attempted to specify an offset that was past the end
5273           of the array passed to splice().  Splicing will instead commence at
5274           the end of the array, rather than past it.  If this isn't what you
5275           want, try explicitly pre-extending the array by assigning $#array =
5276           $offset.  See "splice" in perlfunc.
5277
5278       Split loop
5279           (P) The split was looping infinitely.  (Obviously, a split
5280           shouldn't iterate more times than there are characters of input,
5281           which is what happened.)  See "split" in perlfunc.
5282
5283       Statement unlikely to be reached
5284           (W exec) You did an exec() with some statement after it other than
5285           a die().  This is almost always an error, because exec() never
5286           returns unless there was a failure.  You probably wanted to use
5287           system() instead, which does return.  To suppress this warning, put
5288           the exec() in a block by itself.
5289
5290       "state" subroutine %s can't be in a package
5291           (F) Lexically scoped subroutines aren't in a package, so it doesn't
5292           make sense to try to declare one with a package qualifier on the
5293           front.
5294
5295       "state %s" used in sort comparison
5296           (W syntax) The package variables $a and $b are used for sort
5297           comparisons.  You used $a or $b in as an operand to the "<=>" or
5298           "cmp" operator inside a sort comparison block, and the variable had
5299           earlier been declared as a lexical variable.  Either qualify the
5300           sort variable with the package name, or rename the lexical
5301           variable.
5302
5303       "state" variable %s can't be in a package
5304           (F) Lexically scoped variables aren't in a package, so it doesn't
5305           make sense to try to declare one with a package qualifier on the
5306           front.  Use local() if you want to localize a package variable.
5307
5308       stat() on unopened filehandle %s
5309           (W unopened) You tried to use the stat() function on a filehandle
5310           that was either never opened or has since been closed.
5311
5312       Strings with code points over 0xFF may not be mapped into in-memory
5313       file handles
5314           (W utf8) You tried to open a reference to a scalar for read or
5315           append where the scalar contained code points over 0xFF.  In-memory
5316           files model on-disk files and can only contain bytes.
5317
5318       Stub found while resolving method "%s" overloading "%s" in package "%s"
5319           (P) Overloading resolution over @ISA tree may be broken by
5320           importation stubs.  Stubs should never be implicitly created, but
5321           explicit calls to "can" may break this.
5322
5323       Subroutine attributes must come before the signature
5324           (F) When subroutine signatures are enabled, any subroutine
5325           attributes must come before the signature. Note that this order was
5326           the opposite in versions 5.22..5.26. So:
5327
5328               sub foo :lvalue ($a, $b) { ... }  # 5.20 and 5.28 +
5329               sub foo ($a, $b) :lvalue { ... }  # 5.22 .. 5.26
5330
5331       Subroutine "&%s" is not available
5332           (W closure) During compilation, an inner named subroutine or eval
5333           is attempting to capture an outer lexical subroutine that is not
5334           currently available.  This can happen for one of two reasons.
5335           First, the lexical subroutine may be declared in an outer anonymous
5336           subroutine that has not yet been created.  (Remember that named
5337           subs are created at compile time, while anonymous subs are created
5338           at run-time.)  For example,
5339
5340               sub { my sub a {...} sub f { \&a } }
5341
5342           At the time that f is created, it can't capture the current "a"
5343           sub, since the anonymous subroutine hasn't been created yet.
5344           Conversely, the following won't give a warning since the anonymous
5345           subroutine has by now been created and is live:
5346
5347               sub { my sub a {...} eval 'sub f { \&a }' }->();
5348
5349           The second situation is caused by an eval accessing a lexical
5350           subroutine that has gone out of scope, for example,
5351
5352               sub f {
5353                   my sub a {...}
5354                   sub { eval '\&a' }
5355               }
5356               f()->();
5357
5358           Here, when the '\&a' in the eval is being compiled, f() is not
5359           currently being executed, so its &a is not available for capture.
5360
5361       "%s" subroutine &%s masks earlier declaration in same %s
5362           (W shadow) A "my" or "state" subroutine has been redeclared in the
5363           current scope or statement, effectively eliminating all access to
5364           the previous instance.  This is almost always a typographical
5365           error.  Note that the earlier subroutine will still exist until the
5366           end of the scope or until all closure references to it are
5367           destroyed.
5368
5369       Subroutine %s redefined
5370           (W redefine) You redefined a subroutine.  To suppress this warning,
5371           say
5372
5373               {
5374                   no warnings 'redefine';
5375                   eval "sub name { ... }";
5376               }
5377
5378       Subroutine "%s" will not stay shared
5379           (W closure) An inner (nested) named subroutine is referencing a
5380           "my" subroutine defined in an outer named subroutine.
5381
5382           When the inner subroutine is called, it will see the value of the
5383           outer subroutine's lexical subroutine as it was before and during
5384           the *first* call to the outer subroutine; in this case, after the
5385           first call to the outer subroutine is complete, the inner and outer
5386           subroutines will no longer share a common value for the lexical
5387           subroutine.  In other words, it will no longer be shared.  This
5388           will especially make a difference if the lexical subroutines
5389           accesses lexical variables declared in its surrounding scope.
5390
5391           This problem can usually be solved by making the inner subroutine
5392           anonymous, using the "sub {}" syntax.  When inner anonymous subs
5393           that reference lexical subroutines in outer subroutines are
5394           created, they are automatically rebound to the current values of
5395           such lexical subs.
5396
5397       Substitution loop
5398           (P) The substitution was looping infinitely.  (Obviously, a
5399           substitution shouldn't iterate more times than there are characters
5400           of input, which is what happened.)  See the discussion of
5401           substitution in "Regexp Quote-Like Operators" in perlop.
5402
5403       Substitution pattern not terminated
5404           (F) The lexer couldn't find the interior delimiter of an s/// or
5405           s{}{} construct.  Remember that bracketing delimiters count nesting
5406           level.  Missing the leading "$" from variable $s may cause this
5407           error.
5408
5409       Substitution replacement not terminated
5410           (F) The lexer couldn't find the final delimiter of an s/// or s{}{}
5411           construct.  Remember that bracketing delimiters count nesting
5412           level.  Missing the leading "$" from variable $s may cause this
5413           error.
5414
5415       substr outside of string
5416           (W substr)(F) You tried to reference a substr() that pointed
5417           outside of a string.  That is, the absolute value of the offset was
5418           larger than the length of the string.  See "substr" in perlfunc.
5419           This warning is fatal if substr is used in an lvalue context (as
5420           the left hand side of an assignment or as a subroutine argument for
5421           example).
5422
5423       sv_upgrade from type %d down to type %d
5424           (P) Perl tried to force the upgrade of an SV to a type which was
5425           actually inferior to its current type.
5426
5427       Switch (?(condition)... contains too many branches in regex; marked by
5428       <-- HERE in m/%s/
5429           (F) A (?(condition)if-clause|else-clause) construct can have at
5430           most two branches (the if-clause and the else-clause).  If you want
5431           one or both to contain alternation, such as using
5432           "this|that|other", enclose it in clustering parentheses:
5433
5434               (?(condition)(?:this|that|other)|else-clause)
5435
5436           The <-- HERE shows whereabouts in the regular expression the
5437           problem was discovered.  See perlre.
5438
5439       Switch condition not recognized in regex; marked by <-- HERE in m/%s/
5440           (F) The condition part of a (?(condition)if-clause|else-clause)
5441           construct is not known.  The condition must be one of the
5442           following:
5443
5444            (1) (2) ...        true if 1st, 2nd, etc., capture matched
5445            (<NAME>) ('NAME')  true if named capture matched
5446            (?=...) (?<=...)   true if subpattern matches
5447            (?!...) (?<!...)   true if subpattern fails to match
5448            (?{ CODE })        true if code returns a true value
5449            (R)                true if evaluating inside recursion
5450            (R1) (R2) ...      true if directly inside capture group 1, 2, etc.
5451            (R&NAME)           true if directly inside named capture
5452            (DEFINE)           always false; for defining named subpatterns
5453
5454           The <-- HERE shows whereabouts in the regular expression the
5455           problem was discovered.  See perlre.
5456
5457       Switch (?(condition)... not terminated in regex; marked by <-- HERE in
5458       m/%s/
5459           (F) You omitted to close a (?(condition)...) block somewhere in the
5460           pattern.  Add a closing parenthesis in the appropriate position.
5461           See perlre.
5462
5463       switching effective %s is not implemented
5464           (F) While under the "use filetest" pragma, we cannot switch the
5465           real and effective uids or gids.
5466
5467       syntax error
5468           (F) Probably means you had a syntax error.  Common reasons include:
5469
5470               A keyword is misspelled.
5471               A semicolon is missing.
5472               A comma is missing.
5473               An opening or closing parenthesis is missing.
5474               An opening or closing brace is missing.
5475               A closing quote is missing.
5476
5477           Often there will be another error message associated with the
5478           syntax error giving more information.  (Sometimes it helps to turn
5479           on -w.)  The error message itself often tells you where it was in
5480           the line when it decided to give up.  Sometimes the actual error is
5481           several tokens before this, because Perl is good at understanding
5482           random input.  Occasionally the line number may be misleading, and
5483           once in a blue moon the only way to figure out what's triggering
5484           the error is to call "perl -c" repeatedly, chopping away half the
5485           program each time to see if the error went away.  Sort of the
5486           cybernetic version of 20 questions.
5487
5488       syntax error at line %d: '%s' unexpected
5489           (A) You've accidentally run your script through the Bourne shell
5490           instead of Perl.  Check the #! line, or manually feed your script
5491           into Perl yourself.
5492
5493       syntax error in file %s at line %d, next 2 tokens "%s"
5494           (F) This error is likely to occur if you run a perl5 script through
5495           a perl4 interpreter, especially if the next 2 tokens are "use
5496           strict" or "my $var" or "our $var".
5497
5498       Syntax error in (?[...]) in regex; marked by <-- HERE in m/%s/
5499           (F) Perl could not figure out what you meant inside this construct;
5500           this notifies you that it is giving up trying.
5501
5502       %s syntax OK
5503           (F) The final summary message when a "perl -c" succeeds.
5504
5505       sysread() on closed filehandle %s
5506           (W closed) You tried to read from a closed filehandle.
5507
5508       sysread() on unopened filehandle %s
5509           (W unopened) You tried to read from a filehandle that was never
5510           opened.
5511
5512       System V %s is not implemented on this machine
5513           (F) You tried to do something with a function beginning with "sem",
5514           "shm", or "msg" but that System V IPC is not implemented in your
5515           machine.  In some machines the functionality can exist but be
5516           unconfigured.  Consult your system support.
5517
5518       syswrite() on closed filehandle %s
5519           (W closed) The filehandle you're writing to got itself closed
5520           sometime before now.  Check your control flow.
5521
5522       "-T" and "-B" not implemented on filehandles
5523           (F) Perl can't peek at the stdio buffer of filehandles when it
5524           doesn't know about your kind of stdio.  You'll have to use a
5525           filename instead.
5526
5527       Target of goto is too deeply nested
5528           (F) You tried to use "goto" to reach a label that was too deeply
5529           nested for Perl to reach.  Perl is doing you a favor by refusing.
5530
5531       telldir() attempted on invalid dirhandle %s
5532           (W io) The dirhandle you tried to telldir() is either closed or not
5533           really a dirhandle.  Check your control flow.
5534
5535       tell() on unopened filehandle
5536           (W unopened) You tried to use the tell() function on a filehandle
5537           that was either never opened or has since been closed.
5538
5539       The crypt() function is unimplemented due to excessive paranoia.
5540           (F) Configure couldn't find the crypt() function on your machine,
5541           probably because your vendor didn't supply it, probably because
5542           they think the U.S. Government thinks it's a secret, or at least
5543           that they will continue to pretend that it is.  And if you quote me
5544           on that, I will deny it.
5545
5546       The experimental declared_refs feature is not enabled
5547           (F) To declare references to variables, as in "my \%x", you must
5548           first enable the feature:
5549
5550               no warnings "experimental::declared_refs";
5551               use feature "declared_refs";
5552
5553       The %s function is unimplemented
5554           (F) The function indicated isn't implemented on this architecture,
5555           according to the probings of Configure.
5556
5557       The private_use feature is experimental
5558           (S experimental::private_use) This feature is actually a hook for
5559           future use.
5560
5561       The regex_sets feature is experimental
5562           (S experimental::regex_sets) This warning is emitted if you use the
5563           syntax "(?[   ])" in a regular expression.  The details of this
5564           feature are subject to change.  If you want to use it, but know
5565           that in doing so you are taking the risk of using an experimental
5566           feature which may change in a future Perl version, you can do this
5567           to silence the warning:
5568
5569               no warnings "experimental::regex_sets";
5570
5571       The signatures feature is experimental
5572           (S experimental::signatures) This warning is emitted if you unwrap
5573           a subroutine's arguments using a signature.  Simply suppress the
5574           warning if you want to use the feature, but know that in doing so
5575           you are taking the risk of using an experimental feature which may
5576           change or be removed in a future Perl version:
5577
5578               no warnings "experimental::signatures";
5579               use feature "signatures";
5580               sub foo ($left, $right) { ... }
5581
5582       The stat preceding %s wasn't an lstat
5583           (F) It makes no sense to test the current stat buffer for symbolic
5584           linkhood if the last stat that wrote to the stat buffer already
5585           went past the symlink to get to the real file.  Use an actual
5586           filename instead.
5587
5588       The Unicode property wildcards feature is experimental
5589           (S experimental::uniprop_wildcards) This feature is experimental
5590           and its behavior may in any future release of perl.  See "Wildcards
5591           in Property Values" in perlunicode.
5592
5593       The 'unique' attribute may only be applied to 'our' variables
5594           (F) This attribute was never supported on "my" or "sub"
5595           declarations.
5596
5597       This Perl can't reset CRTL environ elements (%s)
5598       This Perl can't set CRTL environ elements (%s=%s)
5599           (W internal) Warnings peculiar to VMS.  You tried to change or
5600           delete an element of the CRTL's internal environ array, but your
5601           copy of Perl wasn't built with a CRTL that contained the setenv()
5602           function.  You'll need to rebuild Perl with a CRTL that does, or
5603           redefine PERL_ENV_TABLES (see perlvms) so that the environ array
5604           isn't the target of the change to %ENV which produced the warning.
5605
5606       This Perl has not been built with support for randomized hash key
5607       traversal but something called Perl_hv_rand_set().
5608           (F) Something has attempted to use an internal API call which
5609           depends on Perl being compiled with the default support for
5610           randomized hash key traversal, but this Perl has been compiled
5611           without it.  You should report this warning to the relevant
5612           upstream party, or recompile perl with default options.
5613
5614       This use of my() in false conditional is no longer allowed
5615           (F) You used a declaration similar to "my $x if 0".  There has been
5616           a long-standing bug in Perl that causes a lexical variable not to
5617           be cleared at scope exit when its declaration includes a false
5618           conditional.  Some people have exploited this bug to achieve a kind
5619           of static variable.  Since we intend to fix this bug, we don't want
5620           people relying on this behavior.  You can achieve a similar static
5621           effect by declaring the variable in a separate block outside the
5622           function, eg
5623
5624               sub f { my $x if 0; return $x++ }
5625
5626           becomes
5627
5628               { my $x; sub f { return $x++ } }
5629
5630           Beginning with perl 5.10.0, you can also use "state" variables to
5631           have lexicals that are initialized only once (see feature):
5632
5633               sub f { state $x; return $x++ }
5634
5635           This use of "my()" in a false conditional was deprecated beginning
5636           in Perl 5.10 and became a fatal error in Perl 5.30.
5637
5638       Timeout waiting for another thread to define \p{%s}
5639           (F) The first time a user-defined property ("User-Defined Character
5640           Properties" in perlunicode) is used, its definition is looked up
5641           and converted into an internal form for more efficient handling in
5642           subsequent uses.  There could be a race if two or more threads
5643           tried to do this processing nearly simultaneously.  Instead, a
5644           critical section is created around this task, locking out all but
5645           one thread from doing it.  This message indicates that the thread
5646           that is doing the conversion is taking an unexpectedly long time.
5647           The timeout exists solely to prevent deadlock; it's long enough
5648           that the system was likely thrashing and about to crash.  There is
5649           no real remedy but rebooting.
5650
5651       times not implemented
5652           (F) Your version of the C library apparently doesn't do times().  I
5653           suspect you're not running on Unix.
5654
5655       "-T" is on the #! line, it must also be used on the command line
5656           (X) The #! line (or local equivalent) in a Perl script contains the
5657           -T option (or the -t option), but Perl was not invoked with -T in
5658           its command line.  This is an error because, by the time Perl
5659           discovers a -T in a script, it's too late to properly taint
5660           everything from the environment.  So Perl gives up.
5661
5662           If the Perl script is being executed as a command using the #!
5663           mechanism (or its local equivalent), this error can usually be
5664           fixed by editing the #! line so that the -%c option is a part of
5665           Perl's first argument: e.g. change "perl -n -%c" to "perl -%c -n".
5666
5667           If the Perl script is being executed as "perl scriptname", then the
5668           -%c option must appear on the command line: "perl -%c scriptname".
5669
5670       To%s: illegal mapping '%s'
5671           (F) You tried to define a customized To-mapping for lc(), lcfirst,
5672           uc(), or ucfirst() (or their string-inlined versions), but you
5673           specified an illegal mapping.  See "User-Defined Character
5674           Properties" in perlunicode.
5675
5676       Too deeply nested ()-groups
5677           (F) Your template contains ()-groups with a ridiculously deep
5678           nesting level.
5679
5680       Too few args to syscall
5681           (F) There has to be at least one argument to syscall() to specify
5682           the system call to call, silly dilly.
5683
5684       Too few arguments for subroutine '%s' (got %d; expected %d)
5685           (F) A subroutine using a signature fewer arguments than required by
5686           the signature.  The caller of the subroutine is presumably at
5687           fault.
5688
5689           The message attempts to include the name of the called subroutine.
5690           If the subroutine has been aliased, the subroutine's original name
5691           will be shown, regardless of what name the caller used. It will
5692           also indicate the number of arguments given and the number
5693           expected.
5694
5695       Too few arguments for subroutine '%s' (got %d; expected at least %d)
5696           Similar to the previous message but for subroutines that accept a
5697           variable number of arguments.
5698
5699       Too late for "-%s" option
5700           (X) The #! line (or local equivalent) in a Perl script contains the
5701           -M, -m or -C option.
5702
5703           In the case of -M and -m, this is an error because those options
5704           are not intended for use inside scripts.  Use the "use" pragma
5705           instead.
5706
5707           The -C option only works if it is specified on the command line as
5708           well (with the same sequence of letters or numbers following).
5709           Either specify this option on the command line, or, if your system
5710           supports it, make your script executable and run it directly
5711           instead of passing it to perl.
5712
5713       Too late to run %s block
5714           (W void) A CHECK or INIT block is being defined during run time
5715           proper, when the opportunity to run them has already passed.
5716           Perhaps you are loading a file with "require" or "do" when you
5717           should be using "use" instead.  Or perhaps you should put the
5718           "require" or "do" inside a BEGIN block.
5719
5720       Too many args to syscall
5721           (F) Perl supports a maximum of only 14 args to syscall().
5722
5723       Too many arguments for %s
5724           (F) The function requires fewer arguments than you specified.
5725
5726       Too many arguments for subroutine '%s' (got %d; expected %d)
5727           (F) A subroutine using a signature received more arguments than
5728           permitted by the signature.  The caller of the subroutine is
5729           presumably at fault.
5730
5731           The message attempts to include the name of the called subroutine.
5732           If the subroutine has been aliased, the subroutine's original name
5733           will be shown, regardless of what name the caller used. It will
5734           also indicate the number of arguments given and the number
5735           expected.
5736
5737       Too many arguments for subroutine '%s' (got %d; expected at most %d)
5738           Similar to the previous message but for subroutines that accept a
5739           variable number of arguments.
5740
5741       Too many nested open parens in regex; marked by <-- HERE in m/%s/
5742           (F) You have exceeded the number of open "(" parentheses that
5743           haven't been matched by corresponding closing ones.  This limit
5744           prevents eating up too much memory.  It is initially set to 1000,
5745           but may be changed by setting "${^RE_COMPILE_RECURSION_LIMIT}" to
5746           some other value.  This may need to be done in a BEGIN block before
5747           the regular expression pattern is compiled.
5748
5749       Too many )'s
5750           (A) You've accidentally run your script through csh instead of
5751           Perl.  Check the #! line, or manually feed your script into Perl
5752           yourself.
5753
5754       Too many ('s
5755           (A) You've accidentally run your script through csh instead of
5756           Perl.  Check the #! line, or manually feed your script into Perl
5757           yourself.
5758
5759       Trailing \ in regex m/%s/
5760           (F) The regular expression ends with an unbackslashed backslash.
5761           Backslash it.   See perlre.
5762
5763       Transliteration pattern not terminated
5764           (F) The lexer couldn't find the interior delimiter of a tr/// or
5765           tr[][] or y/// or y[][] construct.  Missing the leading "$" from
5766           variables $tr or $y may cause this error.
5767
5768       Transliteration replacement not terminated
5769           (F) The lexer couldn't find the final delimiter of a tr///, tr[][],
5770           y/// or y[][] construct.
5771
5772       '%s' trapped by operation mask
5773           (F) You tried to use an operator from a Safe compartment in which
5774           it's disallowed.  See Safe.
5775
5776       truncate not implemented
5777           (F) Your machine doesn't implement a file truncation mechanism that
5778           Configure knows about.
5779
5780       try/catch is experimental
5781           (S experimental::try) This warning is emitted if you use the "try"
5782           and "catch" syntax. This syntax is currently experimental and its
5783           behaviour may change in future releases of Perl.
5784
5785       Type of arg %d to &CORE::%s must be %s
5786           (F) The subroutine in question in the CORE package requires its
5787           argument to be a hard reference to data of the specified type.
5788           Overloading is ignored, so a reference to an object that is not the
5789           specified type, but nonetheless has overloading to handle it, will
5790           still not be accepted.
5791
5792       Type of arg %d to %s must be %s (not %s)
5793           (F) This function requires the argument in that position to be of a
5794           certain type.  Arrays must be @NAME or "@{EXPR}".  Hashes must be
5795           %NAME or "%{EXPR}".  No implicit dereferencing is allowed--use the
5796           {EXPR} forms as an explicit dereference.  See perlref.
5797
5798       umask not implemented
5799           (F) Your machine doesn't implement the umask function and you tried
5800           to use it to restrict permissions for yourself (EXPR & 0700).
5801
5802       Unbalanced context: %d more PUSHes than POPs
5803           (S internal) The exit code detected an internal inconsistency in
5804           how many execution contexts were entered and left.
5805
5806       Unbalanced saves: %d more saves than restores
5807           (S internal) The exit code detected an internal inconsistency in
5808           how many values were temporarily localized.
5809
5810       Unbalanced scopes: %d more ENTERs than LEAVEs
5811           (S internal) The exit code detected an internal inconsistency in
5812           how many blocks were entered and left.
5813
5814       Unbalanced string table refcount: (%d) for "%s"
5815           (S internal) On exit, Perl found some strings remaining in the
5816           shared string table used for copy on write and for hash keys.  The
5817           entries should have been freed, so this indicates a bug somewhere.
5818
5819       Unbalanced tmps: %d more allocs than frees
5820           (S internal) The exit code detected an internal inconsistency in
5821           how many mortal scalars were allocated and freed.
5822
5823       Undefined format "%s" called
5824           (F) The format indicated doesn't seem to exist.  Perhaps it's
5825           really in another package?  See perlform.
5826
5827       Undefined sort subroutine "%s" called
5828           (F) The sort comparison routine specified doesn't seem to exist.
5829           Perhaps it's in a different package?  See "sort" in perlfunc.
5830
5831       Undefined subroutine &%s called
5832           (F) The subroutine indicated hasn't been defined, or if it was, it
5833           has since been undefined.
5834
5835       Undefined subroutine called
5836           (F) The anonymous subroutine you're trying to call hasn't been
5837           defined, or if it was, it has since been undefined.
5838
5839       Undefined subroutine in sort
5840           (F) The sort comparison routine specified is declared but doesn't
5841           seem to have been defined yet.  See "sort" in perlfunc.
5842
5843       Undefined top format "%s" called
5844           (F) The format indicated doesn't seem to exist.  Perhaps it's
5845           really in another package?  See perlform.
5846
5847       Undefined value assigned to typeglob
5848           (W misc) An undefined value was assigned to a typeglob, a la "*foo
5849           = undef".  This does nothing.  It's possible that you really mean
5850           "undef *foo".
5851
5852       %s: Undefined variable
5853           (A) You've accidentally run your script through csh instead of
5854           Perl.  Check the #! line, or manually feed your script into Perl
5855           yourself.
5856
5857       Unescaped left brace in regex is illegal here in regex; marked by
5858       <-- HERE in m/%s/
5859           (F) The simple rule to remember, if you want to match a literal "{"
5860           character (U+007B "LEFT CURLY BRACKET") in a regular expression
5861           pattern, is to escape each literal instance of it in some way.
5862           Generally easiest is to precede it with a backslash, like "\{" or
5863           enclose it in square brackets ("[{]").  If the pattern delimiters
5864           are also braces, any matching right brace ("}") should also be
5865           escaped to avoid confusing the parser, for example,
5866
5867            qr{abc\{def\}ghi}
5868
5869           Forcing literal "{" characters to be escaped enables the Perl
5870           language to be extended in various ways in future releases.  To
5871           avoid needlessly breaking existing code, the restriction is not
5872           enforced in contexts where there are unlikely to ever be extensions
5873           that could conflict with the use there of "{" as a literal.  Those
5874           that are not potentially ambiguous do not warn; those that are do
5875           raise a non-deprecation warning.
5876
5877           The contexts where no warnings or errors are raised are:
5878
5879           •   as the first character in a pattern, or following "^"
5880               indicating to anchor the match to the beginning of a line.
5881
5882           •   as the first character following a "|" indicating alternation.
5883
5884           •   as the first character in a parenthesized grouping like
5885
5886                /foo({bar)/
5887                /foo(?:{bar)/
5888
5889           •   as the first character following a quantifier
5890
5891                /\s*{/
5892
5893       Unescaped left brace in regex is passed through in regex; marked by
5894       <-- HERE in m/%s/
5895           (W regexp)  The simple rule to remember, if you want to match a
5896           literal "{" character (U+007B "LEFT CURLY BRACKET") in a regular
5897           expression pattern, is to escape each literal instance of it in
5898           some way.  Generally easiest is to precede it with a backslash,
5899           like "\{" or enclose it in square brackets ("[{]").  If the pattern
5900           delimiters are also braces, any matching right brace ("}") should
5901           also be escaped to avoid confusing the parser, for example,
5902
5903            qr{abc\{def\}ghi}
5904
5905           Forcing literal "{" characters to be escaped enables the Perl
5906           language to be extended in various ways in future releases.  To
5907           avoid needlessly breaking existing code, the restriction is not
5908           enforced in contexts where there are unlikely to ever be extensions
5909           that could conflict with the use there of "{" as a literal.  Those
5910           that are not potentially ambiguous do not warn; those that are
5911           raise this warning.  This makes sure that an inadvertent typo
5912           doesn't silently cause the pattern to compile to something
5913           unintended.
5914
5915           The contexts where no warnings or errors are raised are:
5916
5917           •   as the first character in a pattern, or following "^"
5918               indicating to anchor the match to the beginning of a line.
5919
5920           •   as the first character following a "|" indicating alternation.
5921
5922           •   as the first character in a parenthesized grouping like
5923
5924                /foo({bar)/
5925                /foo(?:{bar)/
5926
5927           •   as the first character following a quantifier
5928
5929                /\s*{/
5930
5931       Unescaped literal '%c' in regex; marked by <-- HERE in m/%s/
5932           (W regexp) (only under "use re 'strict'")
5933
5934           Within the scope of "use re 'strict'" in a regular expression
5935           pattern, you included an unescaped "}" or "]" which was interpreted
5936           literally.  These two characters are sometimes metacharacters, and
5937           sometimes literals, depending on what precedes them in the pattern.
5938           This is unlike the similar ")" which is always a metacharacter
5939           unless escaped.
5940
5941           This action at a distance, perhaps a large distance, can lead to
5942           Perl silently misinterpreting what you meant, so when you specify
5943           that you want extra checking by "use re 'strict'", this warning is
5944           generated.  If you meant the character as a literal, simply confirm
5945           that to Perl by preceding the character with a backslash, or make
5946           it into a bracketed character class (like "[}]").  If you meant it
5947           as closing a corresponding "[" or "{", you'll need to look back
5948           through the pattern to find out why that isn't happening.
5949
5950       unexec of %s into %s failed!
5951           (F) The unexec() routine failed for some reason.  See your local
5952           FSF representative, who probably put it there in the first place.
5953
5954       Unexpected binary operator '%c' with no preceding operand in regex;
5955       marked by <-- HERE in m/%s/
5956           (F) You had something like this:
5957
5958            (?[ | \p{Digit} ])
5959
5960           where the "|" is a binary operator with an operand on the right,
5961           but no operand on the left.
5962
5963       Unexpected character in regex; marked by <-- HERE in m/%s/
5964           (F) You had something like this:
5965
5966            (?[ z ])
5967
5968           Within "(?[ ])", no literal characters are allowed unless they are
5969           within an inner pair of square brackets, like
5970
5971            (?[ [ z ] ])
5972
5973           Another possibility is that you forgot a backslash.  Perl isn't
5974           smart enough to figure out what you really meant.
5975
5976       Unexpected constant lvalue entersub entry via type/targ %d:%d
5977           (P) When compiling a subroutine call in lvalue context, Perl failed
5978           an internal consistency check.  It encountered a malformed op tree.
5979
5980       Unexpected exit %u
5981           (S) exit() was called or the script otherwise finished gracefully
5982           when "PERL_EXIT_WARN" was set in "PL_exit_flags".
5983
5984       Unexpected exit failure %d
5985           (S) An uncaught die() was called when "PERL_EXIT_WARN" was set in
5986           "PL_exit_flags".
5987
5988       Unexpected ')' in regex; marked by <-- HERE in m/%s/
5989           (F) You had something like this:
5990
5991            (?[ ( \p{Digit} + ) ])
5992
5993           The ")" is out-of-place.  Something apparently was supposed to be
5994           combined with the digits, or the "+" shouldn't be there, or
5995           something like that.  Perl can't figure out what was intended.
5996
5997       Unexpected ']' with no following ')' in (?[... in regex; marked by <--
5998       HERE in m/%s/
5999           (F) While parsing an extended character class a ']' character was
6000           encountered at a point in the definition where the only legal use
6001           of ']' is to close the character class definition as part of a
6002           '])', you may have forgotten the close paren, or otherwise confused
6003           the parser.
6004
6005       Unexpected '(' with no preceding operator in regex; marked by <-- HERE
6006       in m/%s/
6007           (F) You had something like this:
6008
6009            (?[ \p{Digit} ( \p{Lao} + \p{Thai} ) ])
6010
6011           There should be an operator before the "(", as there's no
6012           indication as to how the digits are to be combined with the
6013           characters in the Lao and Thai scripts.
6014
6015       Unicode non-character U+%X is not recommended for open interchange
6016           (S nonchar) Certain codepoints, such as U+FFFE and U+FFFF, are
6017           defined by the Unicode standard to be non-characters.  Those are
6018           legal codepoints, but are reserved for internal use; so,
6019           applications shouldn't attempt to exchange them.  An application
6020           may not be expecting any of these characters at all, and receiving
6021           them may lead to bugs.  If you know what you are doing you can turn
6022           off this warning by "no warnings 'nonchar';".
6023
6024           This is not really a "severe" error, but it is supposed to be
6025           raised by default even if warnings are not enabled, and currently
6026           the only way to do that in Perl is to mark it as serious.
6027
6028       Unicode property wildcard not terminated
6029           (F) A Unicode property wildcard looks like a delimited regular
6030           expression pattern (all within the braces of the enclosing
6031           "\p{...}".  The closing delimtter to match the opening one was not
6032           found.  If the opening one is escaped by preceding it with a
6033           backslash, the closing one must also be so escaped.
6034
6035       Unicode string properties are not implemented in (?[...]) in regex;
6036       marked by <-- HERE in m/%s/
6037           (F) A Unicode string property is one which expands to a sequence of
6038           multiple characters.  An example is "\p{name=KATAKANA LETTER AINU
6039           P}", which is comprised of the sequence "\N{KATAKANA LETTER SMALL
6040           H}" followed by "\N{COMBINING KATAKANA-HIRAGANA SEMI-VOICED SOUND
6041           MARK}".  Extended character classes, "(?[...])" currently cannot
6042           handle these.
6043
6044       Unicode surrogate U+%X is illegal in UTF-8
6045           (S surrogate) You had a UTF-16 surrogate in a context where they
6046           are not considered acceptable.  These code points, between U+D800
6047           and U+DFFF (inclusive), are used by Unicode only for UTF-16.
6048           However, Perl internally allows all unsigned integer code points
6049           (up to the size limit available on your platform), including
6050           surrogates.  But these can cause problems when being input or
6051           output, which is likely where this message came from.  If you
6052           really really know what you are doing you can turn off this warning
6053           by "no warnings 'surrogate';".
6054
6055       Unknown charname '%s'
6056           (F) The name you used inside "\N{}" is unknown to Perl.  Check the
6057           spelling.  You can say "use charnames ":loose"" to not have to be
6058           so precise about spaces, hyphens, and capitalization on standard
6059           Unicode names.  (Any custom aliases that have been created must be
6060           specified exactly, regardless of whether ":loose" is used or not.)
6061           This error may also happen if the "\N{}" is not in the scope of the
6062           corresponding "use charnames".
6063
6064       Unknown '(*...)' construct '%s' in regex; marked by <-- HERE in m/%s/
6065           (F) The "(*" was followed by something that the regular expression
6066           compiler does not recognize.  Check your spelling.
6067
6068       Unknown error
6069           (P) Perl was about to print an error message in $@, but the $@
6070           variable did not exist, even after an attempt to create it.
6071
6072       Unknown locale category %d; can't set it to %s
6073           (W locale) You used a locale category that perl doesn't recognize,
6074           so it cannot carry out your request.  Check that you are using a
6075           valid category.  If so, see "Multi-threaded" in perllocale for
6076           advice on reporting this as a bug, and for modifying perl locally
6077           to accommodate your needs.
6078
6079       Unknown open() mode '%s'
6080           (F) The second argument of 3-argument open() is not among the list
6081           of valid modes: "<", ">", ">>", "+<", "+>", "+>>", "-|", "|-",
6082           "<&", ">&".
6083
6084       Unknown PerlIO layer "%s"
6085           (W layer) An attempt was made to push an unknown layer onto the
6086           Perl I/O system.  (Layers take care of transforming data between
6087           external and internal representations.)  Note that some layers,
6088           such as "mmap", are not supported in all environments.  If your
6089           program didn't explicitly request the failing operation, it may be
6090           the result of the value of the environment variable PERLIO.
6091
6092       Unknown process %x sent message to prime_env_iter: %s
6093           (P) An error peculiar to VMS.  Perl was reading values for %ENV
6094           before iterating over it, and someone else stuck a message in the
6095           stream of data Perl expected.  Someone's very confused, or perhaps
6096           trying to subvert Perl's population of %ENV for nefarious purposes.
6097
6098       Unknown regexp modifier "/%s"
6099           (F) Alphanumerics immediately following the closing delimiter of a
6100           regular expression pattern are interpreted by Perl as modifier
6101           flags for the regex.  One of the ones you specified is invalid.
6102           One way this can happen is if you didn't put in white space between
6103           the end of the regex and a following alphanumeric operator:
6104
6105            if ($a =~ /foo/and $bar == 3) { ... }
6106
6107           The "a" is a valid modifier flag, but the "n" is not, and raises
6108           this error.  Likely what was meant instead was:
6109
6110            if ($a =~ /foo/ and $bar == 3) { ... }
6111
6112       Unknown "re" subpragma '%s' (known ones are: %s)
6113           (W) You tried to use an unknown subpragma of the "re" pragma.
6114
6115       Unknown switch condition (?(...)) in regex; marked by <-- HERE in m/%s/
6116           (F) The condition part of a (?(condition)if-clause|else-clause)
6117           construct is not known.  The condition must be one of the
6118           following:
6119
6120            (1) (2) ...            true if 1st, 2nd, etc., capture matched
6121            (<NAME>) ('NAME')      true if named capture matched
6122            (?=...) (?<=...)       true if subpattern matches
6123            (*pla:...) (*plb:...)  true if subpattern matches; also
6124                                        (*positive_lookahead:...)
6125                                        (*positive_lookbehind:...)
6126            (*nla:...) (*nlb:...)  true if subpattern fails to match; also
6127                                        (*negative_lookahead:...)
6128                                        (*negative_lookbehind:...)
6129            (?{ CODE })            true if code returns a true value
6130            (R)                    true if evaluating inside recursion
6131            (R1) (R2) ...          true if directly inside capture group 1, 2,
6132                                        etc.
6133            (R&NAME)               true if directly inside named capture
6134            (DEFINE)               always false; for defining named subpatterns
6135
6136           The <-- HERE shows whereabouts in the regular expression the
6137           problem was discovered.  See perlre.
6138
6139       Unknown Unicode option letter '%c'
6140           (F) You specified an unknown Unicode option.  See perlrun
6141           documentation of the "-C" switch for the list of known options.
6142
6143       Unknown Unicode option value %d
6144           (F) You specified an unknown Unicode option.  See perlrun
6145           documentation of the "-C" switch for the list of known options.
6146
6147       Unknown user-defined property name \p{%s}
6148           (F) You specified to use a property within the "\p{...}" which was
6149           a syntactically valid user-defined property, but no definition was
6150           found for it by the time one was required to proceed.  Check your
6151           spelling.  See "User-Defined Character Properties" in perlunicode.
6152
6153       Unknown verb pattern '%s' in regex; marked by <-- HERE in m/%s/
6154           (F) You either made a typo or have incorrectly put a "*" quantifier
6155           after an open brace in your pattern.  Check the pattern and review
6156           perlre for details on legal verb patterns.
6157
6158       Unknown warnings category '%s'
6159           (F) An error issued by the "warnings" pragma.  You specified a
6160           warnings category that is unknown to perl at this point.
6161
6162           Note that if you want to enable a warnings category registered by a
6163           module (e.g. "use warnings 'File::Find'"), you must have loaded
6164           this module first.
6165
6166       Unmatched [ in regex; marked by <-- HERE in m/%s/
6167           (F) The brackets around a character class must match.  If you wish
6168           to include a closing bracket in a character class, backslash it or
6169           put it first.  The <-- HERE shows whereabouts in the regular
6170           expression the problem was discovered.  See perlre.
6171
6172       Unmatched ( in regex; marked by <-- HERE in m/%s/
6173       Unmatched ) in regex; marked by <-- HERE in m/%s/
6174           (F) Unbackslashed parentheses must always be balanced in regular
6175           expressions.  If you're a vi user, the % key is valuable for
6176           finding the matching parenthesis.  The <-- HERE shows whereabouts
6177           in the regular expression the problem was discovered.  See perlre.
6178
6179       Unmatched right %s bracket
6180           (F) The lexer counted more closing curly or square brackets than
6181           opening ones, so you're probably missing a matching opening
6182           bracket.  As a general rule, you'll find the missing one (so to
6183           speak) near the place you were last editing.
6184
6185       Unquoted string "%s" may clash with future reserved word
6186           (W reserved) You used a bareword that might someday be claimed as a
6187           reserved word.  It's best to put such a word in quotes, or
6188           capitalize it somehow, or insert an underbar into it.  You might
6189           also declare it as a subroutine.
6190
6191       Unrecognized character %s; marked by <-- HERE after %s near column %d
6192           (F) The Perl parser has no idea what to do with the specified
6193           character in your Perl script (or eval) near the specified column.
6194           Perhaps you tried  to run a compressed script, a binary program, or
6195           a directory as a Perl program.
6196
6197       Unrecognized escape \%c in character class in regex; marked by <-- HERE
6198       in m/%s/
6199           (F) You used a backslash-character combination which is not
6200           recognized by Perl inside character classes.  This is a fatal error
6201           when the character class is used within "(?[ ])".
6202
6203       Unrecognized escape \%c in character class passed through in regex;
6204       marked by <-- HERE in m/%s/
6205           (W regexp) You used a backslash-character combination which is not
6206           recognized by Perl inside character classes.  The character was
6207           understood literally, but this may change in a future version of
6208           Perl.  The <-- HERE shows whereabouts in the regular expression the
6209           escape was discovered.
6210
6211       Unrecognized escape \%c passed through
6212           (W misc) You used a backslash-character combination which is not
6213           recognized by Perl.  The character was understood literally, but
6214           this may change in a future version of Perl.
6215
6216       Unrecognized escape \%s passed through in regex; marked by <-- HERE in
6217       m/%s/
6218           (W regexp) You used a backslash-character combination which is not
6219           recognized by Perl.  The character(s) were understood literally,
6220           but this may change in a future version of Perl.  The <-- HERE
6221           shows whereabouts in the regular expression the escape was
6222           discovered.
6223
6224       Unrecognized signal name "%s"
6225           (F) You specified a signal name to the kill() function that was not
6226           recognized.  Say "kill -l" in your shell to see the valid signal
6227           names on your system.
6228
6229       Unrecognized switch: -%s  (-h will show valid options)
6230           (F) You specified an illegal option to Perl.  Don't do that.  (If
6231           you think you didn't do that, check the #! line to see if it's
6232           supplying the bad switch on your behalf.)
6233
6234       Unsuccessful %s on filename containing newline
6235           (W newline) A file operation was attempted on a filename, and that
6236           operation failed, PROBABLY because the filename contained a
6237           newline, PROBABLY because you forgot to chomp() it off.  See
6238           "chomp" in perlfunc.
6239
6240       Unsupported directory function "%s" called
6241           (F) Your machine doesn't support opendir() and readdir().
6242
6243       Unsupported function %s
6244           (F) This machine doesn't implement the indicated function,
6245           apparently.  At least, Configure doesn't think so.
6246
6247       Unsupported function fork
6248           (F) Your version of executable does not support forking.
6249
6250           Note that under some systems, like OS/2, there may be different
6251           flavors of Perl executables, some of which may support fork, some
6252           not.  Try changing the name you call Perl by to "perl_", "perl__",
6253           and so on.
6254
6255       Unsupported script encoding %s
6256           (F) Your program file begins with a Unicode Byte Order Mark (BOM)
6257           which declares it to be in a Unicode encoding that Perl cannot
6258           read.
6259
6260       Unsupported socket function "%s" called
6261           (F) Your machine doesn't support the Berkeley socket mechanism, or
6262           at least that's what Configure thought.
6263
6264       Unterminated '(*...' argument in regex; marked by <-- HERE in m/%s/
6265           (F) You used a pattern of the form "(*...:...)" but did not
6266           terminate the pattern with a ")".  Fix the pattern and retry.
6267
6268       Unterminated attribute list
6269           (F) The lexer found something other than a simple identifier at the
6270           start of an attribute, and it wasn't a semicolon or the start of a
6271           block.  Perhaps you terminated the parameter list of the previous
6272           attribute too soon.  See attributes.
6273
6274       Unterminated attribute parameter in attribute list
6275           (F) The lexer saw an opening (left) parenthesis character while
6276           parsing an attribute list, but the matching closing (right)
6277           parenthesis character was not found.  You may need to add (or
6278           remove) a backslash character to get your parentheses to balance.
6279           See attributes.
6280
6281       Unterminated compressed integer
6282           (F) An argument to unpack("w",...) was incompatible with the BER
6283           compressed integer format and could not be converted to an integer.
6284           See "pack" in perlfunc.
6285
6286       Unterminated '(*...' construct in regex; marked by <-- HERE in m/%s/
6287           (F) You used a pattern of the form "(*...)" but did not terminate
6288           the pattern with a ")".  Fix the pattern and retry.
6289
6290       Unterminated delimiter for here document
6291           (F) This message occurs when a here document label has an initial
6292           quotation mark but the final quotation mark is missing.  Perhaps
6293           you wrote:
6294
6295               <<"foo
6296
6297           instead of:
6298
6299               <<"foo"
6300
6301       Unterminated \g... pattern in regex; marked by <-- HERE in m/%s/
6302       Unterminated \g{...} pattern in regex; marked by <-- HERE in m/%s/
6303           (F) In a regular expression, you had a "\g" that wasn't followed by
6304           a proper group reference.  In the case of "\g{", the closing brace
6305           is missing; otherwise the "\g" must be followed by an integer.  Fix
6306           the pattern and retry.
6307
6308       Unterminated <> operator
6309           (F) The lexer saw a left angle bracket in a place where it was
6310           expecting a term, so it's looking for the corresponding right angle
6311           bracket, and not finding it.  Chances are you left some needed
6312           parentheses out earlier in the line, and you really meant a "less
6313           than".
6314
6315       Unterminated verb pattern argument in regex; marked by <-- HERE in
6316       m/%s/
6317           (F) You used a pattern of the form "(*VERB:ARG)" but did not
6318           terminate the pattern with a ")".  Fix the pattern and retry.
6319
6320       Unterminated verb pattern in regex; marked by <-- HERE in m/%s/
6321           (F) You used a pattern of the form "(*VERB)" but did not terminate
6322           the pattern with a ")".  Fix the pattern and retry.
6323
6324       untie attempted while %d inner references still exist
6325           (W untie) A copy of the object returned from "tie" (or "tied") was
6326           still valid when "untie" was called.
6327
6328       Usage: POSIX::%s(%s)
6329           (F) You called a POSIX function with incorrect arguments.  See
6330           "FUNCTIONS" in POSIX for more information.
6331
6332       Usage: Win32::%s(%s)
6333           (F) You called a Win32 function with incorrect arguments.  See
6334           Win32 for more information.
6335
6336       $[ used in %s (did you mean $] ?)
6337           (W syntax) You used $[ in a comparison, such as:
6338
6339               if ($[ > 5.006) {
6340                   ...
6341               }
6342
6343           You probably meant to use $] instead.  $[ is the base for indexing
6344           arrays.  $] is the Perl version number in decimal.
6345
6346       Use "%s" instead of "%s"
6347           (F) The second listed construct is no longer legal.  Use the first
6348           one instead.
6349
6350       Useless assignment to a temporary
6351           (W misc) You assigned to an lvalue subroutine, but what the
6352           subroutine returned was a temporary scalar about to be discarded,
6353           so the assignment had no effect.
6354
6355       Useless (?-%s) - don't use /%s modifier in regex; marked by <-- HERE in
6356       m/%s/
6357           (W regexp) You have used an internal modifier such as (?-o) that
6358           has no meaning unless removed from the entire regexp:
6359
6360               if ($string =~ /(?-o)$pattern/o) { ... }
6361
6362           must be written as
6363
6364               if ($string =~ /$pattern/) { ... }
6365
6366           The <-- HERE shows whereabouts in the regular expression the
6367           problem was discovered.  See perlre.
6368
6369       Useless localization of %s
6370           (W syntax) The localization of lvalues such as "local($x=10)" is
6371           legal, but in fact the local() currently has no effect.  This may
6372           change at some point in the future, but in the meantime such code
6373           is discouraged.
6374
6375       Useless (?%s) - use /%s modifier in regex; marked by <-- HERE in m/%s/
6376           (W regexp) You have used an internal modifier such as (?o) that has
6377           no meaning unless applied to the entire regexp:
6378
6379               if ($string =~ /(?o)$pattern/) { ... }
6380
6381           must be written as
6382
6383               if ($string =~ /$pattern/o) { ... }
6384
6385           The <-- HERE shows whereabouts in the regular expression the
6386           problem was discovered.  See perlre.
6387
6388       Useless use of attribute "const"
6389           (W misc) The "const" attribute has no effect except on anonymous
6390           closure prototypes.  You applied it to a subroutine via
6391           attributes.pm.  This is only useful inside an attribute handler for
6392           an anonymous subroutine.
6393
6394       Useless use of /d modifier in transliteration operator
6395           (W misc) You have used the /d modifier where the searchlist has the
6396           same length as the replacelist.  See perlop for more information
6397           about the /d modifier.
6398
6399       Useless use of \E
6400           (W misc) You have a \E in a double-quotish string without a "\U",
6401           "\L" or "\Q" preceding it.
6402
6403       Useless use of greediness modifier '%c' in regex; marked by <-- HERE in
6404       m/%s/
6405           (W regexp) You specified something like these:
6406
6407            qr/a{3}?/
6408            qr/b{1,1}+/
6409
6410           The "?" and "+" don't have any effect, as they modify whether to
6411           match more or fewer when there is a choice, and by specifying to
6412           match exactly a given numer, there is no room left for a choice.
6413
6414       Useless use of %s in void context
6415           (W void) You did something without a side effect in a context that
6416           does nothing with the return value, such as a statement that
6417           doesn't return a value from a block, or the left side of a scalar
6418           comma operator.  Very often this points not to stupidity on your
6419           part, but a failure of Perl to parse your program the way you
6420           thought it would.  For example, you'd get this if you mixed up your
6421           C precedence with Python precedence and said
6422
6423               $one, $two = 1, 2;
6424
6425           when you meant to say
6426
6427               ($one, $two) = (1, 2);
6428
6429           Another common error is to use ordinary parentheses to construct a
6430           list reference when you should be using square or curly brackets,
6431           for example, if you say
6432
6433               $array = (1,2);
6434
6435           when you should have said
6436
6437               $array = [1,2];
6438
6439           The square brackets explicitly turn a list value into a scalar
6440           value, while parentheses do not.  So when a parenthesized list is
6441           evaluated in a scalar context, the comma is treated like C's comma
6442           operator, which throws away the left argument, which is not what
6443           you want.  See perlref for more on this.
6444
6445           This warning will not be issued for numerical constants equal to 0
6446           or 1 since they are often used in statements like
6447
6448               1 while sub_with_side_effects();
6449
6450           String constants that would normally evaluate to 0 or 1 are warned
6451           about.
6452
6453       Useless use of (?-p) in regex; marked by <-- HERE in m/%s/
6454           (W regexp) The "p" modifier cannot be turned off once set.  Trying
6455           to do so is futile.
6456
6457       Useless use of "re" pragma
6458           (W) You did "use re;" without any arguments.  That isn't very
6459           useful.
6460
6461       Useless use of sort in scalar context
6462           (W void) You used sort in scalar context, as in :
6463
6464               my $x = sort @y;
6465
6466           This is not very useful, and perl currently optimizes this away.
6467
6468       Useless use of %s with no values
6469           (W syntax) You used the push() or unshift() function with no
6470           arguments apart from the array, like "push(@x)" or "unshift(@foo)".
6471           That won't usually have any effect on the array, so is completely
6472           useless.  It's possible in principle that push(@tied_array) could
6473           have some effect if the array is tied to a class which implements a
6474           PUSH method.  If so, you can write it as "push(@tied_array,())" to
6475           avoid this warning.
6476
6477       "use" not allowed in expression
6478           (F) The "use" keyword is recognized and executed at compile time,
6479           and returns no useful value.  See perlmod.
6480
6481       Use of bare << to mean <<"" is forbidden
6482           (F) You are now required to use the explicitly quoted form if you
6483           wish to use an empty line as the terminator of the here-document.
6484
6485           Use of a bare terminator was deprecated in Perl 5.000, and is a
6486           fatal error as of Perl 5.28.
6487
6488       Use of /c modifier is meaningless in s///
6489           (W regexp) You used the /c modifier in a substitution.  The /c
6490           modifier is not presently meaningful in substitutions.
6491
6492       Use of /c modifier is meaningless without /g
6493           (W regexp) You used the /c modifier with a regex operand, but
6494           didn't use the /g modifier.  Currently, /c is meaningful only when
6495           /g is used.  (This may change in the future.)
6496
6497       Use of code point 0x%s is not allowed; the permissible max is 0x%X
6498       Use of code point 0x%s is not allowed; the permissible max is 0x%X in
6499       regex; marked by <-- HERE in m/%s/
6500           (F) You used a code point that is not allowed, because it is too
6501           large.  Unicode only allows code points up to 0x10FFFF, but Perl
6502           allows much larger ones. Earlier versions of Perl allowed code
6503           points above IV_MAX (0x7FFFFFF on 32-bit platforms,
6504           0x7FFFFFFFFFFFFFFF on 64-bit platforms), however, this could
6505           possibly break the perl interpreter in some constructs, including
6506           causing it to hang in a few cases.
6507
6508           If your code is to run on various platforms, keep in mind that the
6509           upper limit depends on the platform.  It is much larger on 64-bit
6510           word sizes than 32-bit ones.
6511
6512           The use of out of range code points was deprecated in Perl 5.24,
6513           and became a fatal error in Perl 5.28.
6514
6515       Use of each() on hash after insertion without resetting hash iterator
6516       results in undefined behavior
6517           (S internal) The behavior of "each()" after insertion is undefined;
6518           it may skip items, or visit items more than once.  Consider using
6519           "keys()" instead of "each()".
6520
6521       Use of := for an empty attribute list is not allowed
6522           (F) The construction "my $x := 42" used to parse as equivalent to
6523           "my $x : = 42" (applying an empty attribute list to $x).  This
6524           construct was deprecated in 5.12.0, and has now been made a syntax
6525           error, so ":=" can be reclaimed as a new operator in the future.
6526
6527           If you need an empty attribute list, for example in a code
6528           generator, add a space before the "=".
6529
6530       Use of %s for non-UTF-8 locale is wrong.  Assuming a UTF-8 locale
6531           (W locale)  You are matching a regular expression using locale
6532           rules, and the specified construct was encountered.  This construct
6533           is only valid for UTF-8 locales, which the current locale isn't.
6534           This doesn't make sense.  Perl will continue, assuming a Unicode
6535           (UTF-8) locale, but the results are likely to be wrong.
6536
6537       Use of freed value in iteration
6538           (F) Perhaps you modified the iterated array within the loop?  This
6539           error is typically caused by code like the following:
6540
6541               @a = (3,4);
6542               @a = () for (1,2,@a);
6543
6544           You are not supposed to modify arrays while they are being iterated
6545           over.  For speed and efficiency reasons, Perl internally does not
6546           do full reference-counting of iterated items, hence deleting such
6547           an item in the middle of an iteration causes Perl to see a freed
6548           value.
6549
6550       Use of /g modifier is meaningless in split
6551           (W regexp) You used the /g modifier on the pattern for a "split"
6552           operator.  Since "split" always tries to match the pattern
6553           repeatedly, the "/g" has no effect.
6554
6555       Use of "goto" to jump into a construct is deprecated
6556           (D deprecated) Using "goto" to jump from an outer scope into an
6557           inner scope is deprecated and should be avoided.
6558
6559           This was deprecated in Perl 5.12.
6560
6561       Use of '%s' in \p{} or \P{} is deprecated because: %s
6562           (D deprecated) Certain properties are deprecated by Unicode, and
6563           may eventually be removed from the Standard, at which time Perl
6564           will follow along.  In the meantime, this message is raised to
6565           notify you.
6566
6567       Use of inherited AUTOLOAD for non-method %s::%s() is no longer allowed
6568           (F) As an accidental feature, "AUTOLOAD" subroutines were looked up
6569           as methods (using the @ISA hierarchy), even when the subroutines to
6570           be autoloaded were called as plain functions (e.g. "Foo::bar()"),
6571           not as methods (e.g. "Foo->bar()" or "$obj->bar()").
6572
6573           This was deprecated in Perl 5.004, and was made fatal in Perl 5.28.
6574
6575       Use of %s in printf format not supported
6576           (F) You attempted to use a feature of printf that is accessible
6577           from only C.  This usually means there's a better way to do it in
6578           Perl.
6579
6580       Use of %s is not allowed in Unicode property wildcard subpatterns in
6581       regex; marked by <-- HERE in m/%s/
6582           (F) You were using a wildcard subpattern a Unicode property value,
6583           and the subpattern contained something that is illegal.  Not all
6584           regular expression capabilities are legal in such subpatterns, and
6585           this is one.  Rewrite your subppattern to not use the offending
6586           construct.  See "Wildcards in Property Values" in perlunicode.
6587
6588       Use of -l on filehandle%s
6589           (W io) A filehandle represents an opened file, and when you opened
6590           the file it already went past any symlink you are presumably trying
6591           to look for.  The operation returned "undef".  Use a filename
6592           instead.
6593
6594       Use of reference "%s" as array index
6595           (W misc) You tried to use a reference as an array index; this
6596           probably isn't what you mean, because references in numerical
6597           context tend to be huge numbers, and so usually indicates
6598           programmer error.
6599
6600           If you really do mean it, explicitly numify your reference, like
6601           so: $array[0+$ref].  This warning is not given for overloaded
6602           objects, however, because you can overload the numification and
6603           stringification operators and then you presumably know what you are
6604           doing.
6605
6606       Use of strings with code points over 0xFF as arguments to %s operator
6607       is not allowed
6608           (F) You tried to use one of the string bitwise operators ("&" or
6609           "|" or "^" or "~") on a string containing a code point over 0xFF.
6610           The string bitwise operators treat their operands as strings of
6611           bytes, and values beyond 0xFF are nonsensical in this context.
6612
6613           Certain instances became fatal in Perl 5.28; others in perl 5.32.
6614
6615       Use of strings with code points over 0xFF as arguments to vec is
6616       forbidden
6617           (F) You tried to use "vec" on a string containing a code point over
6618           0xFF, which is nonsensical here.
6619
6620           This became fatal in Perl 5.32.
6621
6622       Use of tainted arguments in %s is deprecated
6623           (W taint, deprecated) You have supplied "system()" or "exec()" with
6624           multiple arguments and at least one of them is tainted.  This used
6625           to be allowed but will become a fatal error in a future version of
6626           perl.  Untaint your arguments.  See perlsec.
6627
6628       Use of unassigned code point or non-standalone grapheme for a delimiter
6629       is not allowed
6630           (F) A grapheme is what appears to a native-speaker of a language to
6631           be a character.  In Unicode (and hence Perl) a grapheme may
6632           actually be several adjacent characters that together form a
6633           complete grapheme.  For example, there can be a base character,
6634           like "R" and an accent, like a circumflex "^", that appear when
6635           displayed to be a single character with the circumflex hovering
6636           over the "R".  Perl currently allows things like that circumflex to
6637           be delimiters of strings, patterns, etc.  When displayed, the
6638           circumflex would look like it belongs to the character just to the
6639           left of it.  In order to move the language to be able to accept
6640           graphemes as delimiters, we cannot allow the use of delimiters
6641           which aren't graphemes by themselves.  Also, a delimiter must
6642           already be assigned (or known to be never going to be assigned) to
6643           try to future-proof code, for otherwise code that works today would
6644           fail to compile if the currently unassigned delimiter ends up being
6645           something that isn't a stand-alone grapheme.  Because Unicode is
6646           never going to assign non-character code points, nor code points
6647           that are above the legal Unicode maximum, those can be delimiters,
6648           and their use is legal.
6649
6650       Use of uninitialized value%s
6651           (W uninitialized) An undefined value was used as if it were already
6652           defined.  It was interpreted as a "" or a 0, but maybe it was a
6653           mistake.  To suppress this warning assign a defined value to your
6654           variables.
6655
6656           To help you figure out what was undefined, perl will try to tell
6657           you the name of the variable (if any) that was undefined.  In some
6658           cases it cannot do this, so it also tells you what operation you
6659           used the undefined value in.  Note, however, that perl optimizes
6660           your program and the operation displayed in the warning may not
6661           necessarily appear literally in your program.  For example, "that
6662           $foo" is usually optimized into ""that " . $foo", and the warning
6663           will refer to the "concatenation (.)" operator, even though there
6664           is no "." in your program.
6665
6666       "use re 'strict'" is experimental
6667           (S experimental::re_strict) The things that are different when a
6668           regular expression pattern is compiled under 'strict' are subject
6669           to change in future Perl releases in incompatible ways.  This means
6670           that a pattern that compiles today may not in a future Perl
6671           release.  This warning is to alert you to that risk.
6672
6673       Use \x{...} for more than two hex characters in regex; marked by
6674       <-- HERE in m/%s/
6675           (F) In a regular expression, you said something like
6676
6677            (?[ [ \xBEEF ] ])
6678
6679           Perl isn't sure if you meant this
6680
6681            (?[ [ \x{BEEF} ] ])
6682
6683           or if you meant this
6684
6685            (?[ [ \x{BE} E F ] ])
6686
6687           You need to add either braces or blanks to disambiguate.
6688
6689       Using just the first character returned by \N{} in character class in
6690       regex; marked by <-- HERE in m/%s/
6691           (W regexp) Named Unicode character escapes "(\N{...})" may return a
6692           multi-character sequence.  Even though a character class is
6693           supposed to match just one character of input, perl will match the
6694           whole thing correctly, except when the class is inverted
6695           ("[^...]"), or the escape is the beginning or final end point of a
6696           range.  For these, what should happen isn't clear at all.  In these
6697           circumstances, Perl discards all but the first character of the
6698           returned sequence, which is not likely what you want.
6699
6700       Using just the single character results returned by \p{} in (?[...]) in
6701       regex; marked by <-- HERE in m/%s/
6702           (W regexp) Extended character classes currently cannot handle
6703           operands that evaluate to more than one character.  These are
6704           removed from the results of the expansion of the "\p{}".
6705
6706           This situation can happen, for example, in
6707
6708            (?[ \p{name=/KATAKANA/} ])
6709
6710           "KATAKANA LETTER AINU P" is a legal Unicode name (technically a
6711           "named sequence"), but it is actually two characters.  The above
6712           expression with match only the Unicode names containing KATAKANA
6713           that represent single characters.
6714
6715       Using /u for '%s' instead of /%s in regex; marked by <-- HERE in m/%s/
6716           (W regexp) You used a Unicode boundary ("\b{...}" or "\B{...}") in
6717           a portion of a regular expression where the character set modifiers
6718           "/a" or "/aa" are in effect.  These two modifiers indicate an ASCII
6719           interpretation, and this doesn't make sense for a Unicode
6720           definition.  The generated regular expression will compile so that
6721           the boundary uses all of Unicode.  No other portion of the regular
6722           expression is affected.
6723
6724       Using !~ with %s doesn't make sense
6725           (F) Using the "!~" operator with "s///r", "tr///r" or "y///r" is
6726           currently reserved for future use, as the exact behavior has not
6727           been decided.  (Simply returning the boolean opposite of the
6728           modified string is usually not particularly useful.)
6729
6730       UTF-16 surrogate U+%X
6731           (S surrogate) You had a UTF-16 surrogate in a context where they
6732           are not considered acceptable.  These code points, between U+D800
6733           and U+DFFF (inclusive), are used by Unicode only for UTF-16.
6734           However, Perl internally allows all unsigned integer code points
6735           (up to the size limit available on your platform), including
6736           surrogates.  But these can cause problems when being input or
6737           output, which is likely where this message came from.  If you
6738           really really know what you are doing you can turn off this warning
6739           by "no warnings 'surrogate';".
6740
6741       Value of %s can be "0"; test with defined()
6742           (W misc) In a conditional expression, you used <HANDLE>, <*>
6743           (glob), "each()", or "readdir()" as a boolean value.  Each of these
6744           constructs can return a value of "0"; that would make the
6745           conditional expression false, which is probably not what you
6746           intended.  When using these constructs in conditional expressions,
6747           test their values with the "defined" operator.
6748
6749       Value of CLI symbol "%s" too long
6750           (W misc) A warning peculiar to VMS.  Perl tried to read the value
6751           of an %ENV element from a CLI symbol table, and found a resultant
6752           string longer than 1024 characters.  The return value has been
6753           truncated to 1024 characters.
6754
6755       Variable "%s" is not available
6756           (W closure) During compilation, an inner named subroutine or eval
6757           is attempting to capture an outer lexical that is not currently
6758           available.  This can happen for one of two reasons.  First, the
6759           outer lexical may be declared in an outer anonymous subroutine that
6760           has not yet been created.  (Remember that named subs are created at
6761           compile time, while anonymous subs are created at run-time.)  For
6762           example,
6763
6764               sub { my $a; sub f { $a } }
6765
6766           At the time that f is created, it can't capture the current value
6767           of $a, since the anonymous subroutine hasn't been created yet.
6768           Conversely, the following won't give a warning since the anonymous
6769           subroutine has by now been created and is live:
6770
6771               sub { my $a; eval 'sub f { $a }' }->();
6772
6773           The second situation is caused by an eval accessing a variable that
6774           has gone out of scope, for example,
6775
6776               sub f {
6777                   my $a;
6778                   sub { eval '$a' }
6779               }
6780               f()->();
6781
6782           Here, when the '$a' in the eval is being compiled, f() is not
6783           currently being executed, so its $a is not available for capture.
6784
6785       Variable "%s" is not imported%s
6786           (S misc) With "use strict" in effect, you referred to a global
6787           variable that you apparently thought was imported from another
6788           module, because something else of the same name (usually a
6789           subroutine) is exported by that module.  It usually means you put
6790           the wrong funny character on the front of your variable. It is also
6791           possible you used an "our" variable whose scope has ended.
6792
6793       Variable length lookbehind not implemented in regex m/%s/
6794           (F) This message no longer should be raised as of Perl 5.30.  It is
6795           retained in this document as a convenience for people using an
6796           earlier Perl version.
6797
6798           In Perl 5.30 and earlier, lookbehind is allowed only for
6799           subexpressions whose length is fixed and known at compile time.
6800           For positive lookbehind, you can use the "\K" regex construct as a
6801           way to get the equivalent functionality.  See (?<=pattern) and \K
6802           in perlre.
6803
6804           Starting in Perl 5.18, there are non-obvious Unicode rules under
6805           "/i" that can match variably, but which you might not think could.
6806           For example, the substring "ss" can match the single character
6807           LATIN SMALL LETTER SHARP S.  Here's a complete list of the current
6808           ones affecting ASCII characters:
6809
6810              ASCII
6811             sequence      Matches single letter under /i
6812               FF          U+FB00 LATIN SMALL LIGATURE FF
6813               FFI         U+FB03 LATIN SMALL LIGATURE FFI
6814               FFL         U+FB04 LATIN SMALL LIGATURE FFL
6815               FI          U+FB01 LATIN SMALL LIGATURE FI
6816               FL          U+FB02 LATIN SMALL LIGATURE FL
6817               SS          U+00DF LATIN SMALL LETTER SHARP S
6818                           U+1E9E LATIN CAPITAL LETTER SHARP S
6819               ST          U+FB06 LATIN SMALL LIGATURE ST
6820                           U+FB05 LATIN SMALL LIGATURE LONG S T
6821
6822           This list is subject to change, but is quite unlikely to.  Each
6823           ASCII sequence can be any combination of upper- and lowercase.
6824
6825           You can avoid this by using a bracketed character class in the
6826           lookbehind assertion, like
6827
6828            (?<![sS]t)
6829            (?<![fF]f[iI])
6830
6831           This fools Perl into not matching the ligatures.
6832
6833           Another option for Perls starting with 5.16, if you only care about
6834           ASCII matches, is to add the "/aa" modifier to the regex.  This
6835           will exclude all these non-obvious matches, thus getting rid of
6836           this message.  You can also say
6837
6838            use if $] ge 5.016, re => '/aa';
6839
6840           to apply "/aa" to all regular expressions compiled within its
6841           scope.  See re.
6842
6843       "%s" variable %s masks earlier declaration in same %s
6844           (W shadow) A "my", "our" or "state" variable has been redeclared in
6845           the current scope or statement, effectively eliminating all access
6846           to the previous instance.  This is almost always a typographical
6847           error.  Note that the earlier variable will still exist until the
6848           end of the scope or until all closure references to it are
6849           destroyed.
6850
6851       Variable syntax
6852           (A) You've accidentally run your script through csh instead of
6853           Perl.  Check the #! line, or manually feed your script into Perl
6854           yourself.
6855
6856       Variable "%s" will not stay shared
6857           (W closure) An inner (nested) named subroutine is referencing a
6858           lexical variable defined in an outer named subroutine.
6859
6860           When the inner subroutine is called, it will see the value of the
6861           outer subroutine's variable as it was before and during the *first*
6862           call to the outer subroutine; in this case, after the first call to
6863           the outer subroutine is complete, the inner and outer subroutines
6864           will no longer share a common value for the variable.  In other
6865           words, the variable will no longer be shared.
6866
6867           This problem can usually be solved by making the inner subroutine
6868           anonymous, using the "sub {}" syntax.  When inner anonymous subs
6869           that reference variables in outer subroutines are created, they are
6870           automatically rebound to the current values of such variables.
6871
6872       vector argument not supported with alpha versions
6873           (S printf) The %vd (s)printf format does not support version
6874           objects with alpha parts.
6875
6876       Verb pattern '%s' has a mandatory argument in regex; marked by <-- HERE
6877       in m/%s/
6878           (F) You used a verb pattern that requires an argument.  Supply an
6879           argument or check that you are using the right verb.
6880
6881       Verb pattern '%s' may not have an argument in regex; marked by <-- HERE
6882       in m/%s/
6883           (F) You used a verb pattern that is not allowed an argument.
6884           Remove the argument or check that you are using the right verb.
6885
6886       Version control conflict marker
6887           (F) The parser found a line starting with "<<<<<<<", ">>>>>>>", or
6888           "=======".  These may be left by a version control system to mark
6889           conflicts after a failed merge operation.
6890
6891       Version number must be a constant number
6892           (P) The attempt to translate a "use Module n.n LIST" statement into
6893           its equivalent "BEGIN" block found an internal inconsistency with
6894           the version number.
6895
6896       Version string '%s' contains invalid data; ignoring: '%s'
6897           (W misc) The version string contains invalid characters at the end,
6898           which are being ignored.
6899
6900       Warning: something's wrong
6901           (W) You passed warn() an empty string (the equivalent of "warn """)
6902           or you called it with no args and $@ was empty.
6903
6904       Warning: unable to close filehandle %s properly
6905           (S) The implicit close() done by an open() got an error indication
6906           on the close().  This usually indicates your file system ran out of
6907           disk space.
6908
6909       Warning: unable to close filehandle properly: %s
6910       Warning: unable to close filehandle %s properly: %s
6911           (S io) There were errors during the implicit close() done on a
6912           filehandle when its reference count reached zero while it was still
6913           open, e.g.:
6914
6915               {
6916                   open my $fh, '>', $file  or die "open: '$file': $!\n";
6917                   print $fh $data or die "print: $!";
6918               } # implicit close here
6919
6920           Because various errors may only be detected by close() (e.g.
6921           buffering could allow the "print" in this example to return true
6922           even when the disk is full), it is dangerous to ignore its result.
6923           So when it happens implicitly, perl will signal errors by warning.
6924
6925           Prior to version 5.22.0, perl ignored such errors, so the common
6926           idiom shown above was liable to cause silent data loss.
6927
6928       Warning: Use of "%s" without parentheses is ambiguous
6929           (S ambiguous) You wrote a unary operator followed by something that
6930           looks like a binary operator that could also have been interpreted
6931           as a term or unary operator.  For instance, if you know that the
6932           rand function has a default argument of 1.0, and you write
6933
6934               rand + 5;
6935
6936           you may THINK you wrote the same thing as
6937
6938               rand() + 5;
6939
6940           but in actual fact, you got
6941
6942               rand(+5);
6943
6944           So put in parentheses to say what you really mean.
6945
6946       when is experimental
6947           (S experimental::smartmatch) "when" depends on smartmatch, which is
6948           experimental.  Additionally, it has several special cases that may
6949           not be immediately obvious, and their behavior may change or even
6950           be removed in any future release of perl.  See the explanation
6951           under "Experimental Details on given and when" in perlsyn.
6952
6953       Wide character in %s
6954           (S utf8) Perl met a wide character (ordinal >255) when it wasn't
6955           expecting one.  This warning is by default on for I/O (like print).
6956
6957           If this warning does come from I/O, the easiest way to quiet it is
6958           simply to add the ":utf8" layer, e.g., "binmode STDOUT, ':utf8'".
6959           Another way to turn off the warning is to add "no warnings 'utf8';"
6960           but that is often closer to cheating.  In general, you are supposed
6961           to explicitly mark the filehandle with an encoding, see open and
6962           "binmode" in perlfunc.
6963
6964           If the warning comes from other than I/O, this diagnostic probably
6965           indicates that incorrect results are being obtained.  You should
6966           examine your code to determine how a wide character is getting to
6967           an operation that doesn't handle them.
6968
6969       Wide character (U+%X) in %s
6970           (W locale) While in a single-byte locale (i.e., a non-UTF-8 one), a
6971           multi-byte character was encountered.   Perl considers this
6972           character to be the specified Unicode code point.  Combining
6973           non-UTF-8 locales and Unicode is dangerous.  Almost certainly some
6974           characters will have two different representations.  For example,
6975           in the ISO 8859-7 (Greek) locale, the code point 0xC3 represents a
6976           Capital Gamma.  But so also does 0x393.  This will make string
6977           comparisons unreliable.
6978
6979           You likely need to figure out how this multi-byte character got
6980           mixed up with your single-byte locale (or perhaps you thought you
6981           had a UTF-8 locale, but Perl disagrees).
6982
6983       Within []-length '%c' not allowed
6984           (F) The count in the (un)pack template may be replaced by
6985           "[TEMPLATE]" only if "TEMPLATE" always matches the same amount of
6986           packed bytes that can be determined from the template alone.  This
6987           is not possible if it contains any of the codes @, /, U, u, w or a
6988           *-length.  Redesign the template.
6989
6990       While trying to resolve method call %s->%s() can not locate package
6991       "%s" yet it is mentioned in @%s::ISA (perhaps you forgot to load "%s"?)
6992           (W syntax) It is possible that the @ISA contains a misspelled or
6993           never loaded package name, which can result in perl choosing an
6994           unexpected parent class's method to resolve the method call. If
6995           this is deliberate you can do something like
6996
6997             @Missing::Package::ISA = ();
6998
6999           to silence the warnings, otherwise you should correct the package
7000           name, or ensure that the package is loaded prior to the method
7001           call.
7002
7003       %s() with negative argument
7004           (S misc) Certain operations make no sense with negative arguments.
7005           Warning is given and the operation is not done.
7006
7007       write() on closed filehandle %s
7008           (W closed) The filehandle you're writing to got itself closed
7009           sometime before now.  Check your control flow.
7010
7011       %s "\x%X" does not map to Unicode
7012           (S utf8) When reading in different encodings, Perl tries to map
7013           everything into Unicode characters.  The bytes you read in are not
7014           legal in this encoding.  For example
7015
7016               utf8 "\xE4" does not map to Unicode
7017
7018           if you try to read in the a-diaereses Latin-1 as UTF-8.
7019
7020       'X' outside of string
7021           (F) You had a (un)pack template that specified a relative position
7022           before the beginning of the string being (un)packed.  See "pack" in
7023           perlfunc.
7024
7025       'x' outside of string in unpack
7026           (F) You had a pack template that specified a relative position
7027           after the end of the string being unpacked.  See "pack" in
7028           perlfunc.
7029
7030       YOU HAVEN'T DISABLED SET-ID SCRIPTS IN THE KERNEL YET!
7031           (F) And you probably never will, because you probably don't have
7032           the sources to your kernel, and your vendor probably doesn't give a
7033           rip about what you want.  There is a vulnerability anywhere that
7034           you have a set-id script, and to close it you need to remove the
7035           set-id bit from the script that you're attempting to run.  To
7036           actually run the script set-id, your best bet is to put a set-id C
7037           wrapper around your script.
7038
7039       You need to quote "%s"
7040           (W syntax) You assigned a bareword as a signal handler name.
7041           Unfortunately, you already have a subroutine of that name declared,
7042           which means that Perl 5 will try to call the subroutine when the
7043           assignment is executed, which is probably not what you want.  (If
7044           it IS what you want, put an & in front.)
7045
7046       Your random numbers are not that random
7047           (F) When trying to initialize the random seed for hashes, Perl
7048           could not get any randomness out of your system.  This usually
7049           indicates Something Very Wrong.
7050
7051       Zero length \N{} in regex; marked by <-- HERE in m/%s/
7052           (F) Named Unicode character escapes ("\N{...}") may return a zero-
7053           length sequence.  Such an escape was used in an extended character
7054           class, i.e.  "(?[...])", or under "use re 'strict'", which is not
7055           permitted.  Check that the correct escape has been used, and the
7056           correct charnames handler is in scope.  The <-- HERE shows
7057           whereabouts in the regular expression the problem was discovered.
7058

SEE ALSO

7060       warnings, diagnostics.
7061
7062
7063
7064perl v5.34.0                      2021-10-18                       PERLDIAG(1)
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