1PERL5180DELTA(1) Perl Programmers Reference Guide PERL5180DELTA(1)
2
6 perl5180delta - what is new for perl v5.18.0
7
9 This document describes differences between the v5.16.0 release and the
10 v5.18.0 release.
11 If you are upgrading from an earlier release such as v5.14.0, first
13 read perl5160delta, which describes differences between v5.14.0 and
14 v5.16.0.
15
17 New mechanism for experimental features
18 Newly-added experimental features will now require this incantation:
19 no warnings "experimental::feature_name";
21 use feature "feature_name"; # would warn without the prev line
22 There is a new warnings category, called "experimental", containing
24 warnings that the feature pragma emits when enabling experimental
25 features.
26 Newly-added experimental features will also be given special warning
28 IDs, which consist of "experimental::" followed by the name of the
29 feature. (The plan is to extend this mechanism eventually to all
30 warnings, to allow them to be enabled or disabled individually, and not
31 just by category.)
32 By saying
34 no warnings "experimental::feature_name";
36 you are taking responsibility for any breakage that future changes to,
38 or removal of, the feature may cause.
39 Since some features (like "~~" or "my $_") now emit experimental
41 warnings, and you may want to disable them in code that is also run on
42 perls that do not recognize these warning categories, consider using
43 the "if" pragma like this:
44 no if $] >= 5.018, warnings => "experimental::feature_name";
46 Existing experimental features may begin emitting these warnings, too.
48 Please consult perlexperiment for information on which features are
49 considered experimental.
50 Hash overhaul
52 Changes to the implementation of hashes in perl v5.18.0 will be one of
53 the most visible changes to the behavior of existing code.
54 By default, two distinct hash variables with identical keys and values
56 may now provide their contents in a different order where it was
57 previously identical.
58 When encountering these changes, the key to cleaning up from them is to
60 accept that hashes are unordered collections and to act accordingly.
61 Hash randomization
63 The seed used by Perl's hash function is now random. This means that
65 the order which keys/values will be returned from functions like
66 "keys()", "values()", and "each()" will differ from run to run.
67 This change was introduced to make Perl's hashes more robust to
69 algorithmic complexity attacks, and also because we discovered that it
70 exposes hash ordering dependency bugs and makes them easier to track
71 down.
72 Toolchain maintainers might want to invest in additional infrastructure
74 to test for things like this. Running tests several times in a row and
75 then comparing results will make it easier to spot hash order
76 dependencies in code. Authors are strongly encouraged not to expose
77 the key order of Perl's hashes to insecure audiences.
78 Further, every hash has its own iteration order, which should make it
80 much more difficult to determine what the current hash seed is.
81 New hash functions
83 Perl v5.18 includes support for multiple hash functions, and changed
85 the default (to ONE_AT_A_TIME_HARD), you can choose a different
86 algorithm by defining a symbol at compile time. For a current list,
87 consult the INSTALL document. Note that as of Perl v5.18 we can only
88 recommend use of the default or SIPHASH. All the others are known to
89 have security issues and are for research purposes only.
90 PERL_HASH_SEED environment variable now takes a hex value
92 "PERL_HASH_SEED" no longer accepts an integer as a parameter; instead
94 the value is expected to be a binary value encoded in a hex string,
95 such as "0xf5867c55039dc724". This is to make the infrastructure
96 support hash seeds of arbitrary lengths, which might exceed that of an
97 integer. (SipHash uses a 16 byte seed.)
98 PERL_PERTURB_KEYS environment variable added
100 The "PERL_PERTURB_KEYS" environment variable allows one to control the
102 level of randomization applied to "keys" and friends.
103 When "PERL_PERTURB_KEYS" is 0, perl will not randomize the key order at
105 all. The chance that "keys" changes due to an insert will be the same
106 as in previous perls, basically only when the bucket size is changed.
107 When "PERL_PERTURB_KEYS" is 1, perl will randomize keys in a non-
109 repeatable way. The chance that "keys" changes due to an insert will be
110 very high. This is the most secure and default mode.
111 When "PERL_PERTURB_KEYS" is 2, perl will randomize keys in a repeatable
113 way. Repeated runs of the same program should produce the same output
114 every time.
115 "PERL_HASH_SEED" implies a non-default "PERL_PERTURB_KEYS" setting.
117 Setting "PERL_HASH_SEED=0" (exactly one 0) implies
118 "PERL_PERTURB_KEYS=0" (hash key randomization disabled); setting
119 "PERL_HASH_SEED" to any other value implies "PERL_PERTURB_KEYS=2"
120 (deterministic and repeatable hash key randomization). Specifying
121 "PERL_PERTURB_KEYS" explicitly to a different level overrides this
122 behavior.
123 Hash::Util::hash_seed() now returns a string
125 Hash::Util::hash_seed() now returns a string instead of an integer.
127 This is to make the infrastructure support hash seeds of arbitrary
128 lengths which might exceed that of an integer. (SipHash uses a 16 byte
129 seed.)
130 Output of PERL_HASH_SEED_DEBUG has been changed
132 The environment variable PERL_HASH_SEED_DEBUG now makes perl show both
134 the hash function perl was built with, and the seed, in hex, in use for
135 that process. Code parsing this output, should it exist, must change to
136 accommodate the new format. Example of the new format:
137 $ PERL_HASH_SEED_DEBUG=1 ./perl -e1
139 HASH_FUNCTION = MURMUR3 HASH_SEED = 0x1476bb9f
140 Upgrade to Unicode 6.2
142 Perl now supports Unicode 6.2. A list of changes from Unicode 6.1 is
143 at <http://www.unicode.org/versions/Unicode6.2.0>.
144 Character name aliases may now include non-Latin1-range characters
146 It is possible to define your own names for characters for use in
147 "\N{...}", "charnames::vianame()", etc. These names can now be
148 comprised of characters from the whole Unicode range. This allows for
149 names to be in your native language, and not just English. Certain
150 restrictions apply to the characters that may be used (you can't define
151 a name that has punctuation in it, for example). See "CUSTOM ALIASES"
152 in charnames.
153 New DTrace probes
155 The following new DTrace probes have been added:
156 • "op-entry"
158 • "loading-file"
160 • "loaded-file"
162 "${^LAST_FH}"
164 This new variable provides access to the filehandle that was last read.
165 This is the handle used by $. and by "tell" and "eof" without
166 arguments.
167 Regular Expression Set Operations
169 This is an experimental feature to allow matching against the union,
170 intersection, etc., of sets of code points, similar to
171 Unicode::Regex::Set. It can also be used to extend "/x" processing to
172 [bracketed] character classes, and as a replacement of user-defined
173 properties, allowing more complex expressions than they do. See
174 "Extended Bracketed Character Classes" in perlrecharclass.
175 Lexical subroutines
177 This new feature is still considered experimental. To enable it:
178 use 5.018;
180 no warnings "experimental::lexical_subs";
181 use feature "lexical_subs";
182 You can now declare subroutines with "state sub foo", "my sub foo", and
184 "our sub foo". ("state sub" requires that the "state" feature be
185 enabled, unless you write it as "CORE::state sub foo".)
186 "state sub" creates a subroutine visible within the lexical scope in
188 which it is declared. The subroutine is shared between calls to the
189 outer sub.
190 "my sub" declares a lexical subroutine that is created each time the
192 enclosing block is entered. "state sub" is generally slightly faster
193 than "my sub".
194 "our sub" declares a lexical alias to the package subroutine of the
196 same name.
197 For more information, see "Lexical Subroutines" in perlsub.
199 Computed Labels
201 The loop controls "next", "last" and "redo", and the special "dump"
202 operator, now allow arbitrary expressions to be used to compute labels
203 at run time. Previously, any argument that was not a constant was
204 treated as the empty string.
205 More CORE:: subs
207 Several more built-in functions have been added as subroutines to the
208 CORE:: namespace - namely, those non-overridable keywords that can be
209 implemented without custom parsers: "defined", "delete", "exists",
210 "glob", "pos", "prototype", "scalar", "split", "study", and "undef".
211 As some of these have prototypes, "prototype('CORE::...')" has been
213 changed to not make a distinction between overridable and non-
214 overridable keywords. This is to make "prototype('CORE::pos')"
215 consistent with "prototype(&CORE::pos)".
216 "kill" with negative signal names
218 "kill" has always allowed a negative signal number, which kills the
219 process group instead of a single process. It has also allowed signal
220 names. But it did not behave consistently, because negative signal
221 names were treated as 0. Now negative signals names like "-INT" are
222 supported and treated the same way as -2 [perl #112990].
223
225 See also: hash overhaul
226 Some of the changes in the hash overhaul were made to enhance security.
227 Please read that section.
228 "Storable" security warning in documentation
230 The documentation for "Storable" now includes a section which warns
231 readers of the danger of accepting Storable documents from untrusted
232 sources. The short version is that deserializing certain types of data
233 can lead to loading modules and other code execution. This is
234 documented behavior and wanted behavior, but this opens an attack
235 vector for malicious entities.
236 "Locale::Maketext" allowed code injection via a malicious template
238 If users could provide a translation string to Locale::Maketext, this
239 could be used to invoke arbitrary Perl subroutines available in the
240 current process.
241 This has been fixed, but it is still possible to invoke any method
243 provided by "Locale::Maketext" itself or a subclass that you are using.
244 One of these methods in turn will invoke the Perl core's "sprintf"
245 subroutine.
246 In summary, allowing users to provide translation strings without
248 auditing them is a bad idea.
249 This vulnerability is documented in CVE-2012-6329.
251 Avoid calling memset with a negative count
253 Poorly written perl code that allows an attacker to specify the count
254 to perl's "x" string repeat operator can already cause a memory
255 exhaustion denial-of-service attack. A flaw in versions of perl before
256 v5.15.5 can escalate that into a heap buffer overrun; coupled with
257 versions of glibc before 2.16, it possibly allows the execution of
258 arbitrary code.
259 The flaw addressed to this commit has been assigned identifier
261 CVE-2012-5195 and was researched by Tim Brown.
262
264 See also: hash overhaul
265 Some of the changes in the hash overhaul are not fully compatible with
266 previous versions of perl. Please read that section.
267 An unknown character name in "\N{...}" is now a syntax error
269 Previously, it warned, and the Unicode REPLACEMENT CHARACTER was
270 substituted. Unicode now recommends that this situation be a syntax
271 error. Also, the previous behavior led to some confusing warnings and
272 behaviors, and since the REPLACEMENT CHARACTER has no use other than as
273 a stand-in for some unknown character, any code that has this problem
274 is buggy.
275 Formerly deprecated characters in "\N{}" character name aliases are now
277 errors.
278 Since v5.12.0, it has been deprecated to use certain characters in
279 user-defined "\N{...}" character names. These now cause a syntax
280 error. For example, it is now an error to begin a name with a digit,
281 such as in
282 my $undraftable = "\N{4F}"; # Syntax error!
284 or to have commas anywhere in the name. See "CUSTOM ALIASES" in
286 charnames.
287 "\N{BELL}" now refers to U+1F514 instead of U+0007
289 Unicode 6.0 reused the name "BELL" for a different code point than it
290 traditionally had meant. Since Perl v5.14, use of this name still
291 referred to U+0007, but would raise a deprecation warning. Now, "BELL"
292 refers to U+1F514, and the name for U+0007 is "ALERT". All the
293 functions in charnames have been correspondingly updated.
294 New Restrictions in Multi-Character Case-Insensitive Matching in Regular
296 Expression Bracketed Character Classes
297 Unicode has now withdrawn their previous recommendation for regular
298 expressions to automatically handle cases where a single character can
299 match multiple characters case-insensitively, for example, the letter
300 LATIN SMALL LETTER SHARP S and the sequence "ss". This is because it
301 turns out to be impracticable to do this correctly in all
302 circumstances. Because Perl has tried to do this as best it can, it
303 will continue to do so. (We are considering an option to turn it off.)
304 However, a new restriction is being added on such matches when they
305 occur in [bracketed] character classes. People were specifying things
306 such as "/[\0-\xff]/i", and being surprised that it matches the two
307 character sequence "ss" (since LATIN SMALL LETTER SHARP S occurs in
308 this range). This behavior is also inconsistent with using a property
309 instead of a range: "\p{Block=Latin1}" also includes LATIN SMALL
310 LETTER SHARP S, but "/[\p{Block=Latin1}]/i" does not match "ss". The
311 new rule is that for there to be a multi-character case-insensitive
312 match within a bracketed character class, the character must be
313 explicitly listed, and not as an end point of a range. This more
314 closely obeys the Principle of Least Astonishment. See "Bracketed
315 Character Classes" in perlrecharclass. Note that a bug [perl #89774],
316 now fixed as part of this change, prevented the previous behavior from
317 working fully.
318 Explicit rules for variable names and identifiers
320 Due to an oversight, single character variable names in v5.16 were
321 completely unrestricted. This opened the door to several kinds of
322 insanity. As of v5.18, these now follow the rules of other
323 identifiers, in addition to accepting characters that match the
324 "\p{POSIX_Punct}" property.
325 There is no longer any difference in the parsing of identifiers
327 specified by using braces versus without braces. For instance, perl
328 used to allow "${foo:bar}" (with a single colon) but not $foo:bar. Now
329 that both are handled by a single code path, they are both treated the
330 same way: both are forbidden. Note that this change is about the range
331 of permissible literal identifiers, not other expressions.
332 Vertical tabs are now whitespace
334 No one could recall why "\s" didn't match "\cK", the vertical tab. Now
335 it does. Given the extreme rarity of that character, very little
336 breakage is expected. That said, here's what it means:
337 "\s" in a regex now matches a vertical tab in all circumstances.
339 Literal vertical tabs in a regex literal are ignored when the "/x"
341 modifier is used.
342 Leading vertical tabs, alone or mixed with other whitespace, are now
344 ignored when interpreting a string as a number. For example:
345 $dec = " \cK \t 123";
347 $hex = " \cK \t 0xF";
348 say 0 + $dec; # was 0 with warning, now 123
350 say int $dec; # was 0, now 123
351 say oct $hex; # was 0, now 15
352 "/(?{})/" and "/(??{})/" have been heavily reworked
354 The implementation of this feature has been almost completely
355 rewritten. Although its main intent is to fix bugs, some behaviors,
356 especially related to the scope of lexical variables, will have
357 changed. This is described more fully in the "Selected Bug Fixes"
358 section.
359 Stricter parsing of substitution replacement
361 It is no longer possible to abuse the way the parser parses "s///e"
362 like this:
363 %_=(_,"Just another ");
365 $_="Perl hacker,\n";
366 s//_}->{_/e;print
367 "given" now aliases the global $_
369 Instead of assigning to an implicit lexical $_, "given" now makes the
370 global $_ an alias for its argument, just like "foreach". However, it
371 still uses lexical $_ if there is lexical $_ in scope (again, just like
372 "foreach") [perl #114020].
373 The smartmatch family of features are now experimental
375 Smart match, added in v5.10.0 and significantly revised in v5.10.1, has
376 been a regular point of complaint. Although there are a number of ways
377 in which it is useful, it has also proven problematic and confusing for
378 both users and implementors of Perl. There have been a number of
379 proposals on how to best address the problem. It is clear that
380 smartmatch is almost certainly either going to change or go away in the
381 future. Relying on its current behavior is not recommended.
382 Warnings will now be issued when the parser sees "~~", "given", or
384 "when". To disable these warnings, you can add this line to the
385 appropriate scope:
386 no if $] >= 5.018, warnings => "experimental::smartmatch";
388 Consider, though, replacing the use of these features, as they may
390 change behavior again before becoming stable.
391 Lexical $_ is now experimental
393 Since it was introduced in Perl v5.10, it has caused much confusion
394 with no obvious solution:
395 • Various modules (e.g., List::Util) expect callback routines to use
397 the global $_. "use List::Util 'first'; my $_; first { $_ == 1 }
398 @list" does not work as one would expect.
399 • A "my $_" declaration earlier in the same file can cause confusing
401 closure warnings.
402 • The "_" subroutine prototype character allows called subroutines to
404 access your lexical $_, so it is not really private after all.
405 • Nevertheless, subroutines with a "(@)" prototype and methods cannot
407 access the caller's lexical $_, unless they are written in XS.
408 • But even XS routines cannot access a lexical $_ declared, not in
410 the calling subroutine, but in an outer scope, iff that subroutine
411 happened not to mention $_ or use any operators that default to $_.
412 It is our hope that lexical $_ can be rehabilitated, but this may cause
414 changes in its behavior. Please use it with caution until it becomes
415 stable.
416 readline() with "$/ = \N" now reads N characters, not N bytes
418 Previously, when reading from a stream with I/O layers such as
419 "encoding", the readline() function, otherwise known as the "<>"
420 operator, would read N bytes from the top-most layer. [perl #79960]
421 Now, N characters are read instead.
423 There is no change in behaviour when reading from streams with no extra
425 layers, since bytes map exactly to characters.
426 Overridden "glob" is now passed one argument
428 "glob" overrides used to be passed a magical undocumented second
429 argument that identified the caller. Nothing on CPAN was using this,
430 and it got in the way of a bug fix, so it was removed. If you really
431 need to identify the caller, see Devel::Callsite on CPAN.
432 Here doc parsing
434 The body of a here document inside a quote-like operator now always
435 begins on the line after the "<<foo" marker. Previously, it was
436 documented to begin on the line following the containing quote-like
437 operator, but that was only sometimes the case [perl #114040].
438 Alphanumeric operators must now be separated from the closing delimiter of
440 regular expressions
441 You may no longer write something like:
442 m/a/and 1
444 Instead you must write
446 m/a/ and 1
448 with whitespace separating the operator from the closing delimiter of
450 the regular expression. Not having whitespace has resulted in a
451 deprecation warning since Perl v5.14.0.
452 qw(...) can no longer be used as parentheses
454 "qw" lists used to fool the parser into thinking they were always
455 surrounded by parentheses. This permitted some surprising
456 constructions such as "foreach $x qw(a b c) {...}", which should really
457 be written "foreach $x (qw(a b c)) {...}". These would sometimes get
458 the lexer into the wrong state, so they didn't fully work, and the
459 similar "foreach qw(a b c) {...}" that one might expect to be permitted
460 never worked at all.
461 This side effect of "qw" has now been abolished. It has been
463 deprecated since Perl v5.13.11. It is now necessary to use real
464 parentheses everywhere that the grammar calls for them.
465 Interaction of lexical and default warnings
467 Turning on any lexical warnings used first to disable all default
468 warnings if lexical warnings were not already enabled:
469 $*; # deprecation warning
471 use warnings "void";
472 $#; # void warning; no deprecation warning
473 Now, the "debugging", "deprecated", "glob", "inplace" and "malloc"
475 warnings categories are left on when turning on lexical warnings
476 (unless they are turned off by "no warnings", of course).
477 This may cause deprecation warnings to occur in code that used to be
479 free of warnings.
480 Those are the only categories consisting only of default warnings.
482 Default warnings in other categories are still disabled by "use
483 warnings "category"", as we do not yet have the infrastructure for
484 controlling individual warnings.
485 "state sub" and "our sub"
487 Due to an accident of history, "state sub" and "our sub" were
488 equivalent to a plain "sub", so one could even create an anonymous sub
489 with "our sub { ... }". These are now disallowed outside of the
490 "lexical_subs" feature. Under the "lexical_subs" feature they have new
491 meanings described in "Lexical Subroutines" in perlsub.
492 Defined values stored in environment are forced to byte strings
494 A value stored in an environment variable has always been stringified
495 when inherited by child processes.
496 In this release, when assigning to %ENV, values are immediately
498 stringified, and converted to be only a byte string.
499 First, it is forced to be only a string. Then if the string is utf8
501 and the equivalent of "utf8::downgrade()" works, that result is used;
502 otherwise, the equivalent of "utf8::encode()" is used, and a warning is
503 issued about wide characters ("Diagnostics").
504 "require" dies for unreadable files
506 When "require" encounters an unreadable file, it now dies. It used to
507 ignore the file and continue searching the directories in @INC [perl
508 #113422].
509 "gv_fetchmeth_*" and SUPER
511 The various "gv_fetchmeth_*" XS functions used to treat a package whose
512 named ended with "::SUPER" specially. A method lookup on the
513 "Foo::SUPER" package would be treated as a "SUPER" method lookup on the
514 "Foo" package. This is no longer the case. To do a "SUPER" lookup,
515 pass the "Foo" stash and the "GV_SUPER" flag.
516 "split"'s first argument is more consistently interpreted
518 After some changes earlier in v5.17, "split"'s behavior has been
519 simplified: if the PATTERN argument evaluates to a string containing
520 one space, it is treated the way that a literal string containing one
521 space once was.
522
524 Module removals
525 The following modules will be removed from the core distribution in a
526 future release, and will at that time need to be installed from CPAN.
527 Distributions on CPAN which require these modules will need to list
528 them as prerequisites.
529 The core versions of these modules will now issue "deprecated"-category
531 warnings to alert you to this fact. To silence these deprecation
532 warnings, install the modules in question from CPAN.
533 Note that these are (with rare exceptions) fine modules that you are
535 encouraged to continue to use. Their disinclusion from core primarily
536 hinges on their necessity to bootstrapping a fully functional, CPAN-
537 capable Perl installation, not usually on concerns over their design.
538 encoding
540 The use of this pragma is now strongly discouraged. It conflates
541 the encoding of source text with the encoding of I/O data,
542 reinterprets escape sequences in source text (a questionable
543 choice), and introduces the UTF-8 bug to all runtime handling of
544 character strings. It is broken as designed and beyond repair.
545 For using non-ASCII literal characters in source text, please refer
547 to utf8. For dealing with textual I/O data, please refer to Encode
548 and open.
549 Archive::Extract
551 B::Lint
552 B::Lint::Debug
553 CPANPLUS and all included "CPANPLUS::*" modules
554 Devel::InnerPackage
555 Log::Message
556 Log::Message::Config
557 Log::Message::Handlers
558 Log::Message::Item
559 Log::Message::Simple
560 Module::Pluggable
561 Module::Pluggable::Object
562 Object::Accessor
563 Pod::LaTeX
564 Term::UI
565 Term::UI::History
566 Deprecated Utilities
568 The following utilities will be removed from the core distribution in a
569 future release as their associated modules have been deprecated. They
570 will remain available with the applicable CPAN distribution.
571 cpanp
573 "cpanp-run-perl"
574 cpan2dist
575 These items are part of the "CPANPLUS" distribution.
576 pod2latex
578 This item is part of the "Pod::LaTeX" distribution.
579 PL_sv_objcount
581 This interpreter-global variable used to track the total number of Perl
582 objects in the interpreter. It is no longer maintained and will be
583 removed altogether in Perl v5.20.
584 Five additional characters should be escaped in patterns with "/x"
586 When a regular expression pattern is compiled with "/x", Perl treats 6
587 characters as white space to ignore, such as SPACE and TAB. However,
588 Unicode recommends 11 characters be treated thusly. We will conform
589 with this in a future Perl version. In the meantime, use of any of the
590 missing characters will raise a deprecation warning, unless turned off.
591 The five characters are:
592 U+0085 NEXT LINE
594 U+200E LEFT-TO-RIGHT MARK
595 U+200F RIGHT-TO-LEFT MARK
596 U+2028 LINE SEPARATOR
597 U+2029 PARAGRAPH SEPARATOR
598 User-defined charnames with surprising whitespace
600 A user-defined character name with trailing or multiple spaces in a row
601 is likely a typo. This now generates a warning when defined, on the
602 assumption that uses of it will be unlikely to include the excess
603 whitespace.
604 Various XS-callable functions are now deprecated
606 All the functions used to classify characters will be removed from a
607 future version of Perl, and should not be used. With participating C
608 compilers (e.g., gcc), compiling any file that uses any of these will
609 generate a warning. These were not intended for public use; there are
610 equivalent, faster, macros for most of them.
611 See "Character classes" in perlapi. The complete list is:
613 "is_uni_alnum", "is_uni_alnumc", "is_uni_alnumc_lc", "is_uni_alnum_lc",
615 "is_uni_alpha", "is_uni_alpha_lc", "is_uni_ascii", "is_uni_ascii_lc",
616 "is_uni_blank", "is_uni_blank_lc", "is_uni_cntrl", "is_uni_cntrl_lc",
617 "is_uni_digit", "is_uni_digit_lc", "is_uni_graph", "is_uni_graph_lc",
618 "is_uni_idfirst", "is_uni_idfirst_lc", "is_uni_lower",
619 "is_uni_lower_lc", "is_uni_print", "is_uni_print_lc", "is_uni_punct",
620 "is_uni_punct_lc", "is_uni_space", "is_uni_space_lc", "is_uni_upper",
621 "is_uni_upper_lc", "is_uni_xdigit", "is_uni_xdigit_lc",
622 "is_utf8_alnum", "is_utf8_alnumc", "is_utf8_alpha", "is_utf8_ascii",
623 "is_utf8_blank", "is_utf8_char", "is_utf8_cntrl", "is_utf8_digit",
624 "is_utf8_graph", "is_utf8_idcont", "is_utf8_idfirst", "is_utf8_lower",
625 "is_utf8_mark", "is_utf8_perl_space", "is_utf8_perl_word",
626 "is_utf8_posix_digit", "is_utf8_print", "is_utf8_punct",
627 "is_utf8_space", "is_utf8_upper", "is_utf8_xdigit", "is_utf8_xidcont",
628 "is_utf8_xidfirst".
629 In addition these three functions that have never worked properly are
631 deprecated: "to_uni_lower_lc", "to_uni_title_lc", and
632 "to_uni_upper_lc".
633 Certain rare uses of backslashes within regexes are now deprecated
635 There are three pairs of characters that Perl recognizes as
636 metacharacters in regular expression patterns: "{}", "[]", and "()".
637 These can be used as well to delimit patterns, as in:
638 m{foo}
640 s(foo)(bar)
641 Since they are metacharacters, they have special meaning to regular
643 expression patterns, and it turns out that you can't turn off that
644 special meaning by the normal means of preceding them with a backslash,
645 if you use them, paired, within a pattern delimited by them. For
646 example, in
647 m{foo\{1,3\}}
649 the backslashes do not change the behavior, and this matches "f o"
651 followed by one to three more occurrences of "o".
652 Usages like this, where they are interpreted as metacharacters, are
654 exceedingly rare; we think there are none, for example, in all of CPAN.
655 Hence, this deprecation should affect very little code. It does give
656 notice, however, that any such code needs to change, which will in turn
657 allow us to change the behavior in future Perl versions so that the
658 backslashes do have an effect, and without fear that we are silently
659 breaking any existing code.
660 Splitting the tokens "(?" and "(*" in regular expressions
662 A deprecation warning is now raised if the "(" and "?" are separated by
663 white space or comments in "(?...)" regular expression constructs.
664 Similarly, if the "(" and "*" are separated in "(*VERB...)"
665 constructs.
666 Pre-PerlIO IO implementations
668 In theory, you can currently build perl without PerlIO. Instead, you'd
669 use a wrapper around stdio or sfio. In practice, this isn't very
670 useful. It's not well tested, and without any support for IO layers or
671 (thus) Unicode, it's not much of a perl. Building without PerlIO will
672 most likely be removed in the next version of perl.
673 PerlIO supports a "stdio" layer if stdio use is desired. Similarly a
675 sfio layer could be produced in the future, if needed.
676
678 • Platforms without support infrastructure
679 Both Windows CE and z/OS have been historically under-maintained,
681 and are currently neither successfully building nor regularly being
682 smoke tested. Efforts are underway to change this situation, but
683 it should not be taken for granted that the platforms are safe and
684 supported. If they do not become buildable and regularly smoked,
685 support for them may be actively removed in future releases. If
686 you have an interest in these platforms and you can lend your time,
687 expertise, or hardware to help support these platforms, please let
688 the perl development effort know by emailing
689 "perl5-porters@perl.org".
690 Some platforms that appear otherwise entirely dead are also on the
692 short list for removal between now and v5.20.0:
693 DG/UX
695 NeXT
696 We also think it likely that current versions of Perl will no
698 longer build AmigaOS, DJGPP, NetWare (natively), OS/2 and Plan 9.
699 If you are using Perl on such a platform and have an interest in
700 ensuring Perl's future on them, please contact us.
701 We believe that Perl has long been unable to build on mixed endian
703 architectures (such as PDP-11s), and intend to remove any remaining
704 support code. Similarly, code supporting the long unmaintained GNU
705 dld will be removed soon if no-one makes themselves known as an
706 active user.
707 • Swapping of $< and $>
709 Perl has supported the idiom of swapping $< and $> (and likewise $(
711 and $)) to temporarily drop permissions since 5.0, like this:
712 ($<, $>) = ($>, $<);
714 However, this idiom modifies the real user/group id, which can have
716 undesirable side-effects, is no longer useful on any platform perl
717 supports and complicates the implementation of these variables and
718 list assignment in general.
719 As an alternative, assignment only to $> is recommended:
721 local $> = $<;
723 See also: Setuid Demystified
725 <http://www.cs.berkeley.edu/~daw/papers/setuid-usenix02.pdf>.
726 • "microperl", long broken and of unclear present purpose, will be
728 removed.
729 • Revamping "\Q" semantics in double-quotish strings when combined
731 with other escapes.
732 There are several bugs and inconsistencies involving combinations
734 of "\Q" and escapes like "\x", "\L", etc., within a "\Q...\E" pair.
735 These need to be fixed, and doing so will necessarily change
736 current behavior. The changes have not yet been settled.
737 • Use of $x, where "x" stands for any actual (non-printing) C0
739 control character will be disallowed in a future Perl version. Use
740 "${x}" instead (where again "x" stands for a control character), or
741 better, $^A , where "^" is a caret (CIRCUMFLEX ACCENT), and "A"
742 stands for any of the characters listed at the end of "OPERATOR
743 DIFFERENCES" in perlebcdic.
744
746 • Lists of lexical variable declarations ("my($x, $y)") are now
747 optimised down to a single op and are hence faster than before.
748 • A new C preprocessor define "NO_TAINT_SUPPORT" was added that, if
750 set, disables Perl's taint support altogether. Using the -T or -t
751 command line flags will cause a fatal error. Beware that both core
752 tests as well as many a CPAN distribution's tests will fail with
753 this change. On the upside, it provides a small performance
754 benefit due to reduced branching.
755 Do not enable this unless you know exactly what you are getting
757 yourself into.
758 • "pack" with constant arguments is now constant folded in most cases
760 [perl #113470].
761 • Speed up in regular expression matching against Unicode properties.
763 The largest gain is for "\X", the Unicode "extended grapheme
764 cluster." The gain for it is about 35% - 40%. Bracketed character
765 classes, e.g., "[0-9\x{100}]" containing code points above 255 are
766 also now faster.
767 • On platforms supporting it, several former macros are now
769 implemented as static inline functions. This should speed things up
770 slightly on non-GCC platforms.
771 • The optimisation of hashes in boolean context has been extended to
773 affect "scalar(%hash)", "%hash ? ... : ...", and "sub { %hash ||
774 ... }".
775 • Filetest operators manage the stack in a fractionally more
777 efficient manner.
778 • Globs used in a numeric context are now numified directly in most
780 cases, rather than being numified via stringification.
781 • The "x" repetition operator is now folded to a single constant at
783 compile time if called in scalar context with constant operands and
784 no parentheses around the left operand.
785
787 New Modules and Pragmata
788 • Config::Perl::V version 0.16 has been added as a dual-lifed module.
789 It provides structured data retrieval of "perl -V" output including
790 information only known to the "perl" binary and not available via
791 Config.
792 Updated Modules and Pragmata
794 For a complete list of updates, run:
795 $ corelist --diff 5.16.0 5.18.0
797 You can substitute your favorite version in place of 5.16.0, too.
799 • Archive::Extract has been upgraded to 0.68.
801 Work around an edge case on Linux with Busybox's unzip.
803 • Archive::Tar has been upgraded to 1.90.
805 ptar now supports the -T option as well as dashless options
807 [rt.cpan.org #75473], [rt.cpan.org #75475].
808 Auto-encode filenames marked as UTF-8 [rt.cpan.org #75474].
810 Don't use "tell" on IO::Zlib handles [rt.cpan.org #64339].
812 Don't try to "chown" on symlinks.
814 • autodie has been upgraded to 2.13.
816 "autodie" now plays nicely with the 'open' pragma.
818 • B has been upgraded to 1.42.
820 The "stashoff" method of COPs has been added. This provides
822 access to an internal field added in perl 5.16 under threaded
823 builds [perl #113034].
824 "B::COP::stashpv" now supports UTF-8 package names and embedded
826 NULs.
827 All "CVf_*" and "GVf_*" and more SV-related flag values are now
829 provided as constants in the "B::" namespace and available for
830 export. The default export list has not changed.
831 This makes the module work with the new pad API.
833 • B::Concise has been upgraded to 0.95.
835 The "-nobanner" option has been fixed, and "format"s can now be
837 dumped. When passed a sub name to dump, it will check also to see
838 whether it is the name of a format. If a sub and a format share
839 the same name, it will dump both.
840 This adds support for the new "OpMAYBE_TRUEBOOL" and "OPpTRUEBOOL"
842 flags.
843 • B::Debug has been upgraded to 1.18.
845 This adds support (experimentally) for "B::PADLIST", which was
847 added in Perl 5.17.4.
848 • B::Deparse has been upgraded to 1.20.
850 Avoid warning when run under "perl -w".
852 It now deparses loop controls with the correct precedence, and
854 multiple statements in a "format" line are also now deparsed
855 correctly.
856 This release suppresses trailing semicolons in formats.
858 This release adds stub deparsing for lexical subroutines.
860 It no longer dies when deparsing "sort" without arguments. It now
862 correctly omits the comma for "system $prog @args" and "exec $prog
863 @args".
864 • bignum, bigint and bigrat have been upgraded to 0.33.
866 The overrides for "hex" and "oct" have been rewritten, eliminating
868 several problems, and making one incompatible change:
869 • Formerly, whichever of "use bigint" or "use bigrat" was
871 compiled later would take precedence over the other, causing
872 "hex" and "oct" not to respect the other pragma when in scope.
873 • Using any of these three pragmata would cause "hex" and "oct"
875 anywhere else in the program to evaluate their arguments in
876 list context and prevent them from inferring $_ when called
877 without arguments.
878 • Using any of these three pragmata would make "oct("1234")"
880 return 1234 (for any number not beginning with 0) anywhere in
881 the program. Now "1234" is translated from octal to decimal,
882 whether within the pragma's scope or not.
883 • The global overrides that facilitate lexical use of "hex" and
885 "oct" now respect any existing overrides that were in place
886 before the new overrides were installed, falling back to them
887 outside of the scope of "use bignum".
888 • "use bignum "hex"", "use bignum "oct"" and similar invocations
890 for bigint and bigrat now export a "hex" or "oct" function,
891 instead of providing a global override.
892 • Carp has been upgraded to 1.29.
894 Carp is no longer confused when "caller" returns undef for a
896 package that has been deleted.
897 The "longmess()" and "shortmess()" functions are now documented.
899 • CGI has been upgraded to 3.63.
901 Unrecognized HTML escape sequences are now handled better,
903 problematic trailing newlines are no longer inserted after <form>
904 tags by "startform()" or "start_form()", and bogus "Insecure
905 Dependency" warnings appearing with some versions of perl are now
906 worked around.
907 • Class::Struct has been upgraded to 0.64.
909 The constructor now respects overridden accessor methods [perl
911 #29230].
912 • Compress::Raw::Bzip2 has been upgraded to 2.060.
914 The misuse of Perl's "magic" API has been fixed.
916 • Compress::Raw::Zlib has been upgraded to 2.060.
918 Upgrade bundled zlib to version 1.2.7.
920 Fix build failures on Irix, Solaris, and Win32, and also when
922 building as C++ [rt.cpan.org #69985], [rt.cpan.org #77030],
923 [rt.cpan.org #75222].
924 The misuse of Perl's "magic" API has been fixed.
926 "compress()", "uncompress()", "memGzip()" and "memGunzip()" have
928 been speeded up by making parameter validation more efficient.
929 • CPAN::Meta::Requirements has been upgraded to 2.122.
931 Treat undef requirements to "from_string_hash" as 0 (with a
933 warning).
934 Added "requirements_for_module" method.
936 • CPANPLUS has been upgraded to 0.9135.
938 Allow adding blib/script to PATH.
940 Save the history between invocations of the shell.
942 Handle multiple "makemakerargs" and "makeflags" arguments better.
944 This resolves issues with the SQLite source engine.
946 • Data::Dumper has been upgraded to 2.145.
948 It has been optimized to only build a seen-scalar hash as
950 necessary, thereby speeding up serialization drastically.
951 Additional tests were added in order to improve statement, branch,
953 condition and subroutine coverage. On the basis of the coverage
954 analysis, some of the internals of Dumper.pm were refactored.
955 Almost all methods are now documented.
956 • DB_File has been upgraded to 1.827.
958 The main Perl module no longer uses the "@_" construct.
960 • Devel::Peek has been upgraded to 1.11.
962 This fixes compilation with C++ compilers and makes the module work
964 with the new pad API.
965 • Digest::MD5 has been upgraded to 2.52.
967 Fix "Digest::Perl::MD5" OO fallback [rt.cpan.org #66634].
969 • Digest::SHA has been upgraded to 5.84.
971 This fixes a double-free bug, which might have caused
973 vulnerabilities in some cases.
974 • DynaLoader has been upgraded to 1.18.
976 This is due to a minor code change in the XS for the VMS
978 implementation.
979 This fixes warnings about using "CODE" sections without an "OUTPUT"
981 section.
982 • Encode has been upgraded to 2.49.
984 The Mac alias x-mac-ce has been added, and various bugs have been
986 fixed in Encode::Unicode, Encode::UTF7 and Encode::GSM0338.
987 • Env has been upgraded to 1.04.
989 Its SPLICE implementation no longer misbehaves in list context.
991 • ExtUtils::CBuilder has been upgraded to 0.280210.
993 Manifest files are now correctly embedded for those versions of
995 VC++ which make use of them. [perl #111782, #111798].
996 A list of symbols to export can now be passed to "link()" when on
998 Windows, as on other OSes [perl #115100].
999 • ExtUtils::ParseXS has been upgraded to 3.18.
1001 The generated C code now avoids unnecessarily incrementing
1003 "PL_amagic_generation" on Perl versions where it's done
1004 automatically (or on current Perl where the variable no longer
1005 exists).
1006 This avoids a bogus warning for initialised XSUB non-parameters
1008 [perl #112776].
1009 • File::Copy has been upgraded to 2.26.
1011 "copy()" no longer zeros files when copying into the same
1013 directory, and also now fails (as it has long been documented to
1014 do) when attempting to copy a file over itself.
1015 • File::DosGlob has been upgraded to 1.10.
1017 The internal cache of file names that it keeps for each caller is
1019 now freed when that caller is freed. This means "use File::DosGlob
1020 'glob'; eval 'scalar <*>'" no longer leaks memory.
1021 • File::Fetch has been upgraded to 0.38.
1023 Added the 'file_default' option for URLs that do not have a file
1025 component.
1026 Use "File::HomeDir" when available, and provide
1028 "PERL5_CPANPLUS_HOME" to override the autodetection.
1029 Always re-fetch CHECKSUMS if "fetchdir" is set.
1031 • File::Find has been upgraded to 1.23.
1033 This fixes inconsistent unixy path handling on VMS.
1035 Individual files may now appear in list of directories to be
1037 searched [perl #59750].
1038 • File::Glob has been upgraded to 1.20.
1040 File::Glob has had exactly the same fix as File::DosGlob. Since it
1042 is what Perl's own "glob" operator itself uses (except on VMS),
1043 this means "eval 'scalar <*>'" no longer leaks.
1044 A space-separated list of patterns return long lists of results no
1046 longer results in memory corruption or crashes. This bug was
1047 introduced in Perl 5.16.0. [perl #114984]
1048 • File::Spec::Unix has been upgraded to 3.40.
1050 "abs2rel" could produce incorrect results when given two relative
1052 paths or the root directory twice [perl #111510].
1053 • File::stat has been upgraded to 1.07.
1055 "File::stat" ignores the filetest pragma, and warns when used in
1057 combination therewith. But it was not warning for "-r". This has
1058 been fixed [perl #111640].
1059 "-p" now works, and does not return false for pipes [perl #111638].
1061 Previously "File::stat"'s overloaded "-x" and "-X" operators did
1063 not give the correct results for directories or executable files
1064 when running as root. They had been treating executable permissions
1065 for root just like for any other user, performing group membership
1066 tests etc for files not owned by root. They now follow the correct
1067 Unix behaviour - for a directory they are always true, and for a
1068 file if any of the three execute permission bits are set then they
1069 report that root can execute the file. Perl's builtin "-x" and "-X"
1070 operators have always been correct.
1071 • File::Temp has been upgraded to 0.23
1073 Fixes various bugs involving directory removal. Defers unlinking
1075 tempfiles if the initial unlink fails, which fixes problems on NFS.
1076 • GDBM_File has been upgraded to 1.15.
1078 The undocumented optional fifth parameter to "TIEHASH" has been
1080 removed. This was intended to provide control of the callback used
1081 by "gdbm*" functions in case of fatal errors (such as filesystem
1082 problems), but did not work (and could never have worked). No code
1083 on CPAN even attempted to use it. The callback is now always the
1084 previous default, "croak". Problems on some platforms with how the
1085 "C" "croak" function is called have also been resolved.
1086 • Hash::Util has been upgraded to 0.15.
1088 "hash_unlocked" and "hashref_unlocked" now returns true if the hash
1090 is unlocked, instead of always returning false [perl #112126].
1091 "hash_unlocked", "hashref_unlocked", "lock_hash_recurse" and
1093 "unlock_hash_recurse" are now exportable [perl #112126].
1094 Two new functions, "hash_locked" and "hashref_locked", have been
1096 added. Oddly enough, these two functions were already exported,
1097 even though they did not exist [perl #112126].
1098 • HTTP::Tiny has been upgraded to 0.025.
1100 Add SSL verification features [github #6], [github #9].
1102 Include the final URL in the response hashref.
1104 Add "local_address" option.
1106 This improves SSL support.
1108 • IO has been upgraded to 1.28.
1110 "sync()" can now be called on read-only file handles [perl #64772].
1112 IO::Socket tries harder to cache or otherwise fetch socket
1114 information.
1115 • IPC::Cmd has been upgraded to 0.80.
1117 Use "POSIX::_exit" instead of "exit" in "run_forked" [rt.cpan.org
1119 #76901].
1120 • IPC::Open3 has been upgraded to 1.13.
1122 The "open3()" function no longer uses "POSIX::close()" to close
1124 file descriptors since that breaks the ref-counting of file
1125 descriptors done by PerlIO in cases where the file descriptors are
1126 shared by PerlIO streams, leading to attempts to close the file
1127 descriptors a second time when any such PerlIO streams are closed
1128 later on.
1129 • Locale::Codes has been upgraded to 3.25.
1131 It includes some new codes.
1133 • Memoize has been upgraded to 1.03.
1135 Fix the "MERGE" cache option.
1137 • Module::Build has been upgraded to 0.4003.
1139 Fixed bug where modules without $VERSION might have a version of
1141 '0' listed in 'provides' metadata, which will be rejected by PAUSE.
1142 Fixed bug in PodParser to allow numerals in module names.
1144 Fixed bug where giving arguments twice led to them becoming arrays,
1146 resulting in install paths like ARRAY(0xdeadbeef)/lib/Foo.pm.
1147 A minor bug fix allows markup to be used around the leading "Name"
1149 in a POD "abstract" line, and some documentation improvements have
1150 been made.
1151 • Module::CoreList has been upgraded to 2.90
1153 Version information is now stored as a delta, which greatly reduces
1155 the size of the CoreList.pm file.
1156 This restores compatibility with older versions of perl and cleans
1158 up the corelist data for various modules.
1159 • Module::Load::Conditional has been upgraded to 0.54.
1161 Fix use of "requires" on perls installed to a path with spaces.
1163 Various enhancements include the new use of Module::Metadata.
1165 • Module::Metadata has been upgraded to 1.000011.
1167 The creation of a Module::Metadata object for a typical module file
1169 has been sped up by about 40%, and some spurious warnings about
1170 $VERSIONs have been suppressed.
1171 • Module::Pluggable has been upgraded to 4.7.
1173 Amongst other changes, triggers are now allowed on events, which
1175 gives a powerful way to modify behaviour.
1176 • Net::Ping has been upgraded to 2.41.
1178 This fixes some test failures on Windows.
1180 • Opcode has been upgraded to 1.25.
1182 Reflect the removal of the boolkeys opcode and the addition of the
1184 clonecv, introcv and padcv opcodes.
1185 • overload has been upgraded to 1.22.
1187 "no overload" now warns for invalid arguments, just like "use
1189 overload".
1190 • PerlIO::encoding has been upgraded to 0.16.
1192 This is the module implementing the ":encoding(...)" I/O layer. It
1194 no longer corrupts memory or crashes when the encoding back-end
1195 reallocates the buffer or gives it a typeglob or shared hash key
1196 scalar.
1197 • PerlIO::scalar has been upgraded to 0.16.
1199 The buffer scalar supplied may now only contain code points 0xFF or
1201 lower. [perl #109828]
1202 • Perl::OSType has been upgraded to 1.003.
1204 This fixes a bug detecting the VOS operating system.
1206 • Pod::Html has been upgraded to 1.18.
1208 The option "--libpods" has been reinstated. It is deprecated, and
1210 its use does nothing other than issue a warning that it is no
1211 longer supported.
1212 Since the HTML files generated by pod2html claim to have a UTF-8
1214 charset, actually write the files out using UTF-8 [perl #111446].
1215 • Pod::Simple has been upgraded to 3.28.
1217 Numerous improvements have been made, mostly to Pod::Simple::XHTML,
1219 which also has a compatibility change: the "codes_in_verbatim"
1220 option is now disabled by default. See cpan/Pod-Simple/ChangeLog
1221 for the full details.
1222 • re has been upgraded to 0.23
1224 Single character [class]es like "/[s]/" or "/[s]/i" are now
1226 optimized as if they did not have the brackets, i.e. "/s/" or
1227 "/s/i".
1228 See note about "op_comp" in the "Internal Changes" section below.
1230 • Safe has been upgraded to 2.35.
1232 Fix interactions with "Devel::Cover".
1234 Don't eval code under "no strict".
1236 • Scalar::Util has been upgraded to version 1.27.
1238 Fix an overloading issue with "sum".
1240 "first" and "reduce" now check the callback first (so &first(1) is
1242 disallowed).
1243 Fix "tainted" on magical values [rt.cpan.org #55763].
1245 Fix "sum" on previously magical values [rt.cpan.org #61118].
1247 Fix reading past the end of a fixed buffer [rt.cpan.org #72700].
1249 • Search::Dict has been upgraded to 1.07.
1251 No longer require "stat" on filehandles.
1253 Use "fc" for casefolding.
1255 • Socket has been upgraded to 2.009.
1257 Constants and functions required for IP multicast source group
1259 membership have been added.
1260 "unpack_sockaddr_in()" and "unpack_sockaddr_in6()" now return just
1262 the IP address in scalar context, and "inet_ntop()" now guards
1263 against incorrect length scalars being passed in.
1264 This fixes an uninitialized memory read.
1266 • Storable has been upgraded to 2.41.
1268 Modifying $_[0] within "STORABLE_freeze" no longer results in
1270 crashes [perl #112358].
1271 An object whose class implements "STORABLE_attach" is now thawed
1273 only once when there are multiple references to it in the structure
1274 being thawed [perl #111918].
1275 Restricted hashes were not always thawed correctly [perl #73972].
1277 Storable would croak when freezing a blessed REF object with a
1279 "STORABLE_freeze()" method [perl #113880].
1280 It can now freeze and thaw vstrings correctly. This causes a
1282 slight incompatible change in the storage format, so the format
1283 version has increased to 2.9.
1284 This contains various bugfixes, including compatibility fixes for
1286 older versions of Perl and vstring handling.
1287 • Sys::Syslog has been upgraded to 0.32.
1289 This contains several bug fixes relating to "getservbyname()",
1291 "setlogsock()"and log levels in "syslog()", together with fixes for
1292 Windows, Haiku-OS and GNU/kFreeBSD. See cpan/Sys-Syslog/Changes
1293 for the full details.
1294 • Term::ANSIColor has been upgraded to 4.02.
1296 Add support for italics.
1298 Improve error handling.
1300 • Term::ReadLine has been upgraded to 1.10. This fixes the use of
1302 the cpan and cpanp shells on Windows in the event that the current
1303 drive happens to contain a \dev\tty file.
1304 • Test::Harness has been upgraded to 3.26.
1306 Fix glob semantics on Win32 [rt.cpan.org #49732].
1308 Don't use "Win32::GetShortPathName" when calling perl [rt.cpan.org
1310 #47890].
1311 Ignore -T when reading shebang [rt.cpan.org #64404].
1313 Handle the case where we don't know the wait status of the test
1315 more gracefully.
1316 Make the test summary 'ok' line overridable so that it can be
1318 changed to a plugin to make the output of prove idempotent.
1319 Don't run world-writable files.
1321 • Text::Tabs and Text::Wrap have been upgraded to 2012.0818. Support
1323 for Unicode combining characters has been added to them both.
1324 • threads::shared has been upgraded to 1.31.
1326 This adds the option to warn about or ignore attempts to clone
1328 structures that can't be cloned, as opposed to just unconditionally
1329 dying in that case.
1330 This adds support for dual-valued values as created by
1332 Scalar::Util::dualvar.
1333 • Tie::StdHandle has been upgraded to 4.3.
1335 "READ" now respects the offset argument to "read" [perl #112826].
1337 • Time::Local has been upgraded to 1.2300.
1339 Seconds values greater than 59 but less than 60 no longer cause
1341 "timegm()" and "timelocal()" to croak.
1342 • Unicode::UCD has been upgraded to 0.53.
1344 This adds a function all_casefolds() that returns all the
1346 casefolds.
1347 • Win32 has been upgraded to 0.47.
1349 New APIs have been added for getting and setting the current code
1351 page.
1352 Removed Modules and Pragmata
1354 • Version::Requirements has been removed from the core distribution.
1355 It is available under a different name: CPAN::Meta::Requirements.
1356
1358 Changes to Existing Documentation
1359 perlcheat
1360 • perlcheat has been reorganized, and a few new sections were added.
1362 perldata
1364 • Now explicitly documents the behaviour of hash initializer lists
1366 that contain duplicate keys.
1367 perldiag
1369 • The explanation of symbolic references being prevented by "strict
1371 refs" now doesn't assume that the reader knows what symbolic
1372 references are.
1373 perlfaq
1375 • perlfaq has been synchronized with version 5.0150040 from CPAN.
1377 perlfunc
1379 • The return value of "pipe" is now documented.
1381 • Clarified documentation of "our".
1383 perlop
1385 • Loop control verbs ("dump", "goto", "next", "last" and "redo") have
1387 always had the same precedence as assignment operators, but this
1388 was not documented until now.
1389 Diagnostics
1391 The following additions or changes have been made to diagnostic output,
1393 including warnings and fatal error messages. For the complete list of
1394 diagnostic messages, see perldiag.
1395 New Diagnostics
1397 New Errors
1398 • Unterminated delimiter for here document
1400 This message now occurs when a here document label has an initial
1402 quotation mark but the final quotation mark is missing.
1403 This replaces a bogus and misleading error message about not
1405 finding the label itself [perl #114104].
1406 • panic: child pseudo-process was never scheduled
1408 This error is thrown when a child pseudo-process in the ithreads
1410 implementation on Windows was not scheduled within the time period
1411 allowed and therefore was not able to initialize properly [perl
1412 #88840].
1413 • Group name must start with a non-digit word character in regex;
1415 marked by <-- HERE in m/%s/
1416 This error has been added for "(?&0)", which is invalid. It used
1418 to produce an incomprehensible error message [perl #101666].
1419 • Can't use an undefined value as a subroutine reference
1421 Calling an undefined value as a subroutine now produces this error
1423 message. It used to, but was accidentally disabled, first in Perl
1424 5.004 for non-magical variables, and then in Perl v5.14 for magical
1425 (e.g., tied) variables. It has now been restored. In the mean
1426 time, undef was treated as an empty string [perl #113576].
1427 • Experimental "%s" subs not enabled
1429 To use lexical subs, you must first enable them:
1431 no warnings 'experimental::lexical_subs';
1433 use feature 'lexical_subs';
1434 my sub foo { ... }
1435 New Warnings
1437 • 'Strings with code points over 0xFF may not be mapped into in-
1439 memory file handles'
1440 • '%s' resolved to '\o{%s}%d'
1442 • 'Trailing white-space in a charnames alias definition is
1444 deprecated'
1445 • 'A sequence of multiple spaces in a charnames alias definition is
1447 deprecated'
1448 • 'Passing malformed UTF-8 to "%s" is deprecated'
1450 • Subroutine "&%s" is not available
1452 (W closure) During compilation, an inner named subroutine or eval
1454 is attempting to capture an outer lexical subroutine that is not
1455 currently available. This can happen for one of two reasons.
1456 First, the lexical subroutine may be declared in an outer anonymous
1457 subroutine that has not yet been created. (Remember that named
1458 subs are created at compile time, while anonymous subs are created
1459 at run-time.) For example,
1460 sub { my sub a {...} sub f { \&a } }
1462 At the time that f is created, it can't capture the current the "a"
1464 sub, since the anonymous subroutine hasn't been created yet.
1465 Conversely, the following won't give a warning since the anonymous
1466 subroutine has by now been created and is live:
1467 sub { my sub a {...} eval 'sub f { \&a }' }->();
1469 The second situation is caused by an eval accessing a variable that
1471 has gone out of scope, for example,
1472 sub f {
1474 my sub a {...}
1475 sub { eval '\&a' }
1476 }
1477 f()->();
1478 Here, when the '\&a' in the eval is being compiled, f() is not
1480 currently being executed, so its &a is not available for capture.
1481 • "%s" subroutine &%s masks earlier declaration in same %s
1483 (W misc) A "my" or "state" subroutine has been redeclared in the
1485 current scope or statement, effectively eliminating all access to
1486 the previous instance. This is almost always a typographical
1487 error. Note that the earlier subroutine will still exist until the
1488 end of the scope or until all closure references to it are
1489 destroyed.
1490 • The %s feature is experimental
1492 (S experimental) This warning is emitted if you enable an
1494 experimental feature via "use feature". Simply suppress the
1495 warning if you want to use the feature, but know that in doing so
1496 you are taking the risk of using an experimental feature which may
1497 change or be removed in a future Perl version:
1498 no warnings "experimental::lexical_subs";
1500 use feature "lexical_subs";
1501 • sleep(%u) too large
1503 (W overflow) You called "sleep" with a number that was larger than
1505 it can reliably handle and "sleep" probably slept for less time
1506 than requested.
1507 • Wide character in setenv
1509 Attempts to put wide characters into environment variables via %ENV
1511 now provoke this warning.
1512 • "Invalid negative number (%s) in chr"
1514 "chr()" now warns when passed a negative value [perl #83048].
1516 • "Integer overflow in srand"
1518 "srand()" now warns when passed a value that doesn't fit in a "UV"
1520 (since the value will be truncated rather than overflowing) [perl
1521 #40605].
1522 • "-i used with no filenames on the command line, reading from STDIN"
1524 Running perl with the "-i" flag now warns if no input files are
1526 provided on the command line [perl #113410].
1527 Changes to Existing Diagnostics
1529 • $* is no longer supported
1530 The warning that use of $* and $# is no longer supported is now
1532 generated for every location that references them. Previously it
1533 would fail to be generated if another variable using the same
1534 typeglob was seen first (e.g. "@*" before $*), and would not be
1535 generated for the second and subsequent uses. (It's hard to fix
1536 the failure to generate warnings at all without also generating
1537 them every time, and warning every time is consistent with the
1538 warnings that $[ used to generate.)
1539 • The warnings for "\b{" and "\B{" were added. They are a
1541 deprecation warning which should be turned off by that category.
1542 One should not have to turn off regular regexp warnings as well to
1543 get rid of these.
1544 • Constant(%s): Call to &{$^H{%s}} did not return a defined value
1546 Constant overloading that returns "undef" results in this error
1548 message. For numeric constants, it used to say "Constant(undef)".
1549 "undef" has been replaced with the number itself.
1550 • The error produced when a module cannot be loaded now includes a
1552 hint that the module may need to be installed: "Can't locate
1553 hopping.pm in @INC (you may need to install the hopping module)
1554 (@INC contains: ...)"
1555 • vector argument not supported with alpha versions
1557 This warning was not suppressible, even with "no warnings". Now it
1559 is suppressible, and has been moved from the "internal" category to
1560 the "printf" category.
1561 • "Can't do {n,m} with n > m in regex; marked by <-- HERE in m/%s/"
1563 This fatal error has been turned into a warning that reads:
1565 Quantifier {n,m} with n > m can't match in regex
1567 (W regexp) Minima should be less than or equal to maxima. If you
1569 really want your regexp to match something 0 times, just put {0}.
1570 • The "Runaway prototype" warning that occurs in bizarre cases has
1572 been removed as being unhelpful and inconsistent.
1573 • The "Not a format reference" error has been removed, as the only
1575 case in which it could be triggered was a bug.
1576 • The "Unable to create sub named %s" error has been removed for the
1578 same reason.
1579 • The 'Can't use "my %s" in sort comparison' error has been
1581 downgraded to a warning, '"my %s" used in sort comparison' (with
1582 'state' instead of 'my' for state variables). In addition, the
1583 heuristics for guessing whether lexical $a or $b has been misused
1584 have been improved to generate fewer false positives. Lexical $a
1585 and $b are no longer disallowed if they are outside the sort block.
1586 Also, a named unary or list operator inside the sort block no
1587 longer causes the $a or $b to be ignored [perl #86136].
1588
1590 h2xs
1591 • h2xs no longer produces invalid code for empty defines. [perl
1593 #20636]
1594
1596 • Added "useversionedarchname" option to Configure
1597 When set, it includes 'api_versionstring' in 'archname'. E.g.
1599 x86_64-linux-5.13.6-thread-multi. It is unset by default.
1600 This feature was requested by Tim Bunce, who observed that
1602 "INSTALL_BASE" creates a library structure that does not
1603 differentiate by perl version. Instead, it places architecture
1604 specific files in "$install_base/lib/perl5/$archname". This makes
1605 it difficult to use a common "INSTALL_BASE" library path with
1606 multiple versions of perl.
1607 By setting "-Duseversionedarchname", the $archname will be distinct
1609 for architecture and API version, allowing mixed use of
1610 "INSTALL_BASE".
1611 • Add a "PERL_NO_INLINE_FUNCTIONS" option
1613 If "PERL_NO_INLINE_FUNCTIONS" is defined, don't include "inline.h"
1615 This permits test code to include the perl headers for definitions
1617 without creating a link dependency on the perl library (which may
1618 not exist yet).
1619 • Configure will honour the external "MAILDOMAIN" environment
1621 variable, if set.
1622 • "installman" no longer ignores the silent option
1624 • Both "META.yml" and "META.json" files are now included in the
1626 distribution.
1627 • Configure will now correctly detect "isblank()" when compiling with
1629 a C++ compiler.
1630 • The pager detection in Configure has been improved to allow
1632 responses which specify options after the program name, e.g.
1633 /usr/bin/less -R, if the user accepts the default value. This
1634 helps perldoc when handling ANSI escapes [perl #72156].
1635
1637 • The test suite now has a section for tests that require very large
1638 amounts of memory. These tests won't run by default; they can be
1639 enabled by setting the "PERL_TEST_MEMORY" environment variable to
1640 the number of gibibytes of memory that may be safely used.
1641
1643 Discontinued Platforms
1644 BeOS
1645 BeOS was an operating system for personal computers developed by Be
1646 Inc, initially for their BeBox hardware. The OS Haiku was written
1647 as an open source replacement for/continuation of BeOS, and its
1648 perl port is current and actively maintained.
1649 UTS Global
1651 Support code relating to UTS global has been removed. UTS was a
1652 mainframe version of System V created by Amdahl, subsequently sold
1653 to UTS Global. The port has not been touched since before Perl
1654 v5.8.0, and UTS Global is now defunct.
1655 VM/ESA
1657 Support for VM/ESA has been removed. The port was tested on 2.3.0,
1658 which IBM ended service on in March 2002. 2.4.0 ended service in
1659 June 2003, and was superseded by Z/VM. The current version of Z/VM
1660 is V6.2.0, and scheduled for end of service on 2015/04/30.
1661 MPE/IX
1663 Support for MPE/IX has been removed.
1664 EPOC
1666 Support code relating to EPOC has been removed. EPOC was a family
1667 of operating systems developed by Psion for mobile devices. It was
1668 the predecessor of Symbian. The port was last updated in April
1669 2002.
1670 Rhapsody
1672 Support for Rhapsody has been removed.
1673 Platform-Specific Notes
1675 AIX
1676 Configure now always adds "-qlanglvl=extc99" to the CC flags on AIX
1678 when using xlC. This will make it easier to compile a number of XS-
1679 based modules that assume C99 [perl #113778].
1680 clang++
1682 There is now a workaround for a compiler bug that prevented compiling
1684 with clang++ since Perl v5.15.7 [perl #112786].
1685 C++
1687 When compiling the Perl core as C++ (which is only semi-supported), the
1689 mathom functions are now compiled as "extern "C"", to ensure proper
1690 binary compatibility. (However, binary compatibility isn't generally
1691 guaranteed anyway in the situations where this would matter.)
1692 Darwin
1694 Stop hardcoding an alignment on 8 byte boundaries to fix builds using
1696 -Dusemorebits.
1697 Haiku
1699 Perl should now work out of the box on Haiku R1 Alpha 4.
1701 MidnightBSD
1703 "libc_r" was removed from recent versions of MidnightBSD and older
1705 versions work better with "pthread". Threading is now enabled using
1706 "pthread" which corrects build errors with threading enabled on
1707 0.4-CURRENT.
1708 Solaris
1710 In Configure, avoid running sed commands with flags not supported on
1712 Solaris.
1713 VMS
1715 • Where possible, the case of filenames and command-line arguments is
1717 now preserved by enabling the CRTL features
1718 "DECC$EFS_CASE_PRESERVE" and "DECC$ARGV_PARSE_STYLE" at start-up
1719 time. The latter only takes effect when extended parse is enabled
1720 in the process from which Perl is run.
1721 • The character set for Extended Filename Syntax (EFS) is now enabled
1723 by default on VMS. Among other things, this provides better
1724 handling of dots in directory names, multiple dots in filenames,
1725 and spaces in filenames. To obtain the old behavior, set the
1726 logical name "DECC$EFS_CHARSET" to "DISABLE".
1727 • Fixed linking on builds configured with "-Dusemymalloc=y".
1729 • Experimental support for building Perl with the HP C++ compiler is
1731 available by configuring with "-Dusecxx".
1732 • All C header files from the top-level directory of the distribution
1734 are now installed on VMS, providing consistency with a long-
1735 standing practice on other platforms. Previously only a subset were
1736 installed, which broke non-core extension builds for extensions
1737 that depended on the missing include files.
1738 • Quotes are now removed from the command verb (but not the
1740 parameters) for commands spawned via "system", backticks, or a
1741 piped "open". Previously, quotes on the verb were passed through
1742 to DCL, which would fail to recognize the command. Also, if the
1743 verb is actually a path to an image or command procedure on an
1744 ODS-5 volume, quoting it now allows the path to contain spaces.
1745 • The a2p build has been fixed for the HP C++ compiler on OpenVMS.
1747 Win32
1749 • Perl can now be built using Microsoft's Visual C++ 2012 compiler by
1751 specifying CCTYPE=MSVC110 (or MSVC110FREE if you are using the free
1752 Express edition for Windows Desktop) in win32/Makefile.
1753 • The option to build without "USE_SOCKETS_AS_HANDLES" has been
1755 removed.
1756 • Fixed a problem where perl could crash while cleaning up threads
1758 (including the main thread) in threaded debugging builds on Win32
1759 and possibly other platforms [perl #114496].
1760 • A rare race condition that would lead to sleep taking more time
1762 than requested, and possibly even hanging, has been fixed [perl
1763 #33096].
1764 • "link" on Win32 now attempts to set $! to more appropriate values
1766 based on the Win32 API error code. [perl #112272]
1767 Perl no longer mangles the environment block, e.g. when launching a
1769 new sub-process, when the environment contains non-ASCII
1770 characters. Known problems still remain, however, when the
1771 environment contains characters outside of the current ANSI
1772 codepage (e.g. see the item about Unicode in %ENV in
1773 <http://perl5.git.perl.org/perl.git/blob/HEAD:/Porting/todo.pod>).
1774 [perl #113536]
1775 • Building perl with some Windows compilers used to fail due to a
1777 problem with miniperl's "glob" operator (which uses the "perlglob"
1778 program) deleting the PATH environment variable [perl #113798].
1779 • A new makefile option, "USE_64_BIT_INT", has been added to the
1781 Windows makefiles. Set this to "define" when building a 32-bit
1782 perl if you want it to use 64-bit integers.
1783 Machine code size reductions, already made to the DLLs of XS
1785 modules in Perl v5.17.2, have now been extended to the perl DLL
1786 itself.
1787 Building with VC++ 6.0 was inadvertently broken in Perl v5.17.2 but
1789 has now been fixed again.
1790 WinCE
1792 Building on WinCE is now possible once again, although more work is
1794 required to fully restore a clean build.
1795
1797 • Synonyms for the misleadingly named "av_len()" have been created:
1798 "av_top_index()" and "av_tindex". All three of these return the
1799 number of the highest index in the array, not the number of
1800 elements it contains.
1801 • SvUPGRADE() is no longer an expression. Originally this macro (and
1803 its underlying function, sv_upgrade()) were documented as boolean,
1804 although in reality they always croaked on error and never returned
1805 false. In 2005 the documentation was updated to specify a void
1806 return value, but SvUPGRADE() was left always returning 1 for
1807 backwards compatibility. This has now been removed, and SvUPGRADE()
1808 is now a statement with no return value.
1809 So this is now a syntax error:
1811 if (!SvUPGRADE(sv)) { croak(...); }
1813 If you have code like that, simply replace it with
1815 SvUPGRADE(sv);
1817 or to avoid compiler warnings with older perls, possibly
1819 (void)SvUPGRADE(sv);
1821 • Perl has a new copy-on-write mechanism that allows any SvPOK scalar
1823 to be upgraded to a copy-on-write scalar. A reference count on the
1824 string buffer is stored in the string buffer itself. This feature
1825 is not enabled by default.
1826 It can be enabled in a perl build by running Configure with
1828 -Accflags=-DPERL_NEW_COPY_ON_WRITE, and we would encourage XS
1829 authors to try their code with such an enabled perl, and provide
1830 feedback. Unfortunately, there is not yet a good guide to updating
1831 XS code to cope with COW. Until such a document is available,
1832 consult the perl5-porters mailing list.
1833 It breaks a few XS modules by allowing copy-on-write scalars to go
1835 through code paths that never encountered them before.
1836 • Copy-on-write no longer uses the SvFAKE and SvREADONLY flags.
1838 Hence, SvREADONLY indicates a true read-only SV.
1839 Use the SvIsCOW macro (as before) to identify a copy-on-write
1841 scalar.
1842 • "PL_glob_index" is gone.
1844 • The private Perl_croak_no_modify has had its context parameter
1846 removed. It is now has a void prototype. Users of the public API
1847 croak_no_modify remain unaffected.
1848 • Copy-on-write (shared hash key) scalars are no longer marked read-
1850 only. "SvREADONLY" returns false on such an SV, but "SvIsCOW"
1851 still returns true.
1852 • A new op type, "OP_PADRANGE" has been introduced. The perl
1854 peephole optimiser will, where possible, substitute a single
1855 padrange op for a pushmark followed by one or more pad ops, and
1856 possibly also skipping list and nextstate ops. In addition, the op
1857 can carry out the tasks associated with the RHS of a "my(...) = @_"
1858 assignment, so those ops may be optimised away too.
1859 • Case-insensitive matching inside a [bracketed] character class with
1861 a multi-character fold no longer excludes one of the possibilities
1862 in the circumstances that it used to. [perl #89774].
1863 • "PL_formfeed" has been removed.
1865 • The regular expression engine no longer reads one byte past the end
1867 of the target string. While for all internally well-formed scalars
1868 this should never have been a problem, this change facilitates
1869 clever tricks with string buffers in CPAN modules. [perl #73542]
1870 • Inside a BEGIN block, "PL_compcv" now points to the currently-
1872 compiling subroutine, rather than the BEGIN block itself.
1873 • "mg_length" has been deprecated.
1875 • "sv_len" now always returns a byte count and "sv_len_utf8" a
1877 character count. Previously, "sv_len" and "sv_len_utf8" were both
1878 buggy and would sometimes returns bytes and sometimes characters.
1879 "sv_len_utf8" no longer assumes that its argument is in UTF-8.
1880 Neither of these creates UTF-8 caches for tied or overloaded values
1881 or for non-PVs any more.
1882 • "sv_mortalcopy" now copies string buffers of shared hash key
1884 scalars when called from XS modules [perl #79824].
1885 • The new "RXf_MODIFIES_VARS" flag can be set by custom regular
1887 expression engines to indicate that the execution of the regular
1888 expression may cause variables to be modified. This lets "s///"
1889 know to skip certain optimisations. Perl's own regular expression
1890 engine sets this flag for the special backtracking verbs that set
1891 $REGMARK and $REGERROR.
1892 • The APIs for accessing lexical pads have changed considerably.
1894 "PADLIST"s are now longer "AV"s, but their own type instead.
1896 "PADLIST"s now contain a "PAD" and a "PADNAMELIST" of "PADNAME"s,
1897 rather than "AV"s for the pad and the list of pad names. "PAD"s,
1898 "PADNAMELIST"s, and "PADNAME"s are to be accessed as such through
1899 the newly added pad API instead of the plain "AV" and "SV" APIs.
1900 See perlapi for details.
1901 • In the regex API, the numbered capture callbacks are passed an
1903 index indicating what match variable is being accessed. There are
1904 special index values for the "$`, $&, $&" variables. Previously the
1905 same three values were used to retrieve "${^PREMATCH}, ${^MATCH},
1906 ${^POSTMATCH}" too, but these have now been assigned three separate
1907 values. See "Numbered capture callbacks" in perlreapi.
1908 • "PL_sawampersand" was previously a boolean indicating that any of
1910 "$`, $&, $&" had been seen; it now contains three one-bit flags
1911 indicating the presence of each of the variables individually.
1912 • The "CV *" typemap entry now supports "&{}" overloading and
1914 typeglobs, just like "&{...}" [perl #96872].
1915 • The "SVf_AMAGIC" flag to indicate overloading is now on the stash,
1917 not the object. It is now set automatically whenever a method or
1918 @ISA changes, so its meaning has changed, too. It now means
1919 "potentially overloaded". When the overload table is calculated,
1920 the flag is automatically turned off if there is no overloading, so
1921 there should be no noticeable slowdown.
1922 The staleness of the overload tables is now checked when overload
1924 methods are invoked, rather than during "bless".
1925 "A" magic is gone. The changes to the handling of the "SVf_AMAGIC"
1927 flag eliminate the need for it.
1928 "PL_amagic_generation" has been removed as no longer necessary.
1930 For XS modules, it is now a macro alias to "PL_na".
1931 The fallback overload setting is now stored in a stash entry
1933 separate from overloadedness itself.
1934 • The character-processing code has been cleaned up in places. The
1936 changes should be operationally invisible.
1937 • The "study" function was made a no-op in v5.16. It was simply
1939 disabled via a "return" statement; the code was left in place. Now
1940 the code supporting what "study" used to do has been removed.
1941 • Under threaded perls, there is no longer a separate PV allocated
1943 for every COP to store its package name ("cop->stashpv"). Instead,
1944 there is an offset ("cop->stashoff") into the new "PL_stashpad"
1945 array, which holds stash pointers.
1946 • In the pluggable regex API, the "regexp_engine" struct has acquired
1948 a new field "op_comp", which is currently just for perl's internal
1949 use, and should be initialized to NULL by other regex plugin
1950 modules.
1951 • A new function "alloccopstash" has been added to the API, but is
1953 considered experimental. See perlapi.
1954 • Perl used to implement get magic in a way that would sometimes hide
1956 bugs in code that could call mg_get() too many times on magical
1957 values. This hiding of errors no longer occurs, so long-standing
1958 bugs may become visible now. If you see magic-related errors in XS
1959 code, check to make sure it, together with the Perl API functions
1960 it uses, calls mg_get() only once on SvGMAGICAL() values.
1961 • OP allocation for CVs now uses a slab allocator. This simplifies
1963 memory management for OPs allocated to a CV, so cleaning up after a
1964 compilation error is simpler and safer [perl #111462][perl
1965 #112312].
1966 • "PERL_DEBUG_READONLY_OPS" has been rewritten to work with the new
1968 slab allocator, allowing it to catch more violations than before.
1969 • The old slab allocator for ops, which was only enabled for
1971 "PERL_IMPLICIT_SYS" and "PERL_DEBUG_READONLY_OPS", has been
1972 retired.
1973
1975 • Here document terminators no longer require a terminating newline
1976 character when they occur at the end of a file. This was already
1977 the case at the end of a string eval [perl #65838].
1978 • "-DPERL_GLOBAL_STRUCT" builds now free the global struct after
1980 they've finished using it.
1981 • A trailing '/' on a path in @INC will no longer have an additional
1983 '/' appended.
1984 • The ":crlf" layer now works when unread data doesn't fit into its
1986 own buffer. [perl #112244].
1987 • "ungetc()" now handles UTF-8 encoded data. [perl #116322].
1989 • A bug in the core typemap caused any C types that map to the T_BOOL
1991 core typemap entry to not be set, updated, or modified when the
1992 T_BOOL variable was used in an OUTPUT: section with an exception
1993 for RETVAL. T_BOOL in an INPUT: section was not affected. Using a
1994 T_BOOL return type for an XSUB (RETVAL) was not affected. A side
1995 effect of fixing this bug is, if a T_BOOL is specified in the
1996 OUTPUT: section (which previous did nothing to the SV), and a read
1997 only SV (literal) is passed to the XSUB, croaks like "Modification
1998 of a read-only value attempted" will happen. [perl #115796]
1999 • On many platforms, providing a directory name as the script name
2001 caused perl to do nothing and report success. It should now
2002 universally report an error and exit nonzero. [perl #61362]
2003 • "sort {undef} ..." under fatal warnings no longer crashes. It had
2005 begun crashing in Perl v5.16.
2006 • Stashes blessed into each other ("bless \%Foo::, 'Bar'; bless
2008 \%Bar::, 'Foo'") no longer result in double frees. This bug
2009 started happening in Perl v5.16.
2010 • Numerous memory leaks have been fixed, mostly involving fatal
2012 warnings and syntax errors.
2013 • Some failed regular expression matches such as "'f' =~ /../g" were
2015 not resetting "pos". Also, "match-once" patterns ("m?...?g")
2016 failed to reset it, too, when invoked a second time [perl #23180].
2017 • Several bugs involving "local *ISA" and "local *Foo::" causing
2019 stale MRO caches have been fixed.
2020 • Defining a subroutine when its typeglob has been aliased no longer
2022 results in stale method caches. This bug was introduced in Perl
2023 v5.10.
2024 • Localising a typeglob containing a subroutine when the typeglob's
2026 package has been deleted from its parent stash no longer produces
2027 an error. This bug was introduced in Perl v5.14.
2028 • Under some circumstances, "local *method=..." would fail to reset
2030 method caches upon scope exit.
2031 • "/[.foo.]/" is no longer an error, but produces a warning (as
2033 before) and is treated as "/[.fo]/" [perl #115818].
2034 • "goto $tied_var" now calls FETCH before deciding what type of goto
2036 (subroutine or label) this is.
2037 • Renaming packages through glob assignment ("*Foo:: = *Bar::; *Bar::
2039 = *Baz::") in combination with "m?...?" and "reset" no longer makes
2040 threaded builds crash.
2041 • A number of bugs related to assigning a list to hash have been
2043 fixed. Many of these involve lists with repeated keys like "(1, 1,
2044 1, 1)".
2045 • The expression "scalar(%h = (1, 1, 1, 1))" now returns 4, not
2047 2.
2048 • The return value of "%h = (1, 1, 1)" in list context was wrong.
2050 Previously this would return "(1, undef, 1)", now it returns
2051 "(1, undef)".
2052 • Perl now issues the same warning on "($s, %h) = (1, {})" as it
2054 does for "(%h) = ({})", "Reference found where even-sized list
2055 expected".
2056 • A number of additional edge cases in list assignment to hashes
2058 were corrected. For more details see commit 23b7025ebc.
2059 • Attributes applied to lexical variables no longer leak memory.
2061 [perl #114764]
2062 • "dump", "goto", "last", "next", "redo" or "require" followed by a
2064 bareword (or version) and then an infix operator is no longer a
2065 syntax error. It used to be for those infix operators (like "+")
2066 that have a different meaning where a term is expected. [perl
2067 #105924]
2068 • "require a::b . 1" and "require a::b + 1" no longer produce
2070 erroneous ambiguity warnings. [perl #107002]
2071 • Class method calls are now allowed on any string, and not just
2073 strings beginning with an alphanumeric character. [perl #105922]
2074 • An empty pattern created with "qr//" used in "m///" no longer
2076 triggers the "empty pattern reuses last pattern" behaviour. [perl
2077 #96230]
2078 • Tying a hash during iteration no longer results in a memory leak.
2080 • Freeing a tied hash during iteration no longer results in a memory
2082 leak.
2083 • List assignment to a tied array or hash that dies on STORE no
2085 longer results in a memory leak.
2086 • If the hint hash ("%^H") is tied, compile-time scope entry (which
2088 copies the hint hash) no longer leaks memory if FETCH dies. [perl
2089 #107000]
2090 • Constant folding no longer inappropriately triggers the special
2092 "split " "" behaviour. [perl #94490]
2093 • "defined scalar(@array)", "defined do { &foo }", and similar
2095 constructs now treat the argument to "defined" as a simple scalar.
2096 [perl #97466]
2097 • Running a custom debugging that defines no *DB::DB glob or provides
2099 a subroutine stub for &DB::DB no longer results in a crash, but an
2100 error instead. [perl #114990]
2101 • "reset """ now matches its documentation. "reset" only resets
2103 "m?...?" patterns when called with no argument. An empty string
2104 for an argument now does nothing. (It used to be treated as no
2105 argument.) [perl #97958]
2106 • "printf" with an argument returning an empty list no longer reads
2108 past the end of the stack, resulting in erratic behaviour. [perl
2109 #77094]
2110 • "--subname" no longer produces erroneous ambiguity warnings. [perl
2112 #77240]
2113 • "v10" is now allowed as a label or package name. This was
2115 inadvertently broken when v-strings were added in Perl v5.6. [perl
2116 #56880]
2117 • "length", "pos", "substr" and "sprintf" could be confused by ties,
2119 overloading, references and typeglobs if the stringification of
2120 such changed the internal representation to or from UTF-8. [perl
2121 #114410]
2122 • utf8::encode now calls FETCH and STORE on tied variables.
2124 utf8::decode now calls STORE (it was already calling FETCH).
2125 • "$tied =~ s/$non_utf8/$utf8/" no longer loops infinitely if the
2127 tied variable returns a Latin-1 string, shared hash key scalar, or
2128 reference or typeglob that stringifies as ASCII or Latin-1. This
2129 was a regression from v5.12.
2130 • "s///" without /e is now better at detecting when it needs to
2132 forego certain optimisations, fixing some buggy cases:
2133 • Match variables in certain constructs ("&&", "||", ".." and
2135 others) in the replacement part; e.g., "s/(.)/$l{$a||$1}/g".
2136 [perl #26986]
2137 • Aliases to match variables in the replacement.
2139 • $REGERROR or $REGMARK in the replacement. [perl #49190]
2141 • An empty pattern ("s//$foo/") that causes the last-successful
2143 pattern to be used, when that pattern contains code blocks that
2144 modify the variables in the replacement.
2145 • The taintedness of the replacement string no longer affects the
2147 taintedness of the return value of "s///e".
2148 • The $| autoflush variable is created on-the-fly when needed. If
2150 this happened (e.g., if it was mentioned in a module or eval) when
2151 the currently-selected filehandle was a typeglob with an empty IO
2152 slot, it used to crash. [perl #115206]
2153 • Line numbers at the end of a string eval are no longer off by one.
2155 [perl #114658]
2156 • @INC filters (subroutines returned by subroutines in @INC) that set
2158 $_ to a copy-on-write scalar no longer cause the parser to modify
2159 that string buffer in place.
2160 • "length($object)" no longer returns the undefined value if the
2162 object has string overloading that returns undef. [perl #115260]
2163 • The use of "PL_stashcache", the stash name lookup cache for method
2165 calls, has been restored,
2166 Commit da6b625f78f5f133 in August 2011 inadvertently broke the code
2168 that looks up values in "PL_stashcache". As it's only a cache,
2169 quite correctly everything carried on working without it.
2170 • The error "Can't localize through a reference" had disappeared in
2172 v5.16.0 when "local %$ref" appeared on the last line of an lvalue
2173 subroutine. This error disappeared for "\local %$ref" in perl
2174 v5.8.1. It has now been restored.
2175 • The parsing of here-docs has been improved significantly, fixing
2177 several parsing bugs and crashes and one memory leak, and
2178 correcting wrong subsequent line numbers under certain conditions.
2179 • Inside an eval, the error message for an unterminated here-doc no
2181 longer has a newline in the middle of it [perl #70836].
2182 • A substitution inside a substitution pattern ("s/${s|||}//") no
2184 longer confuses the parser.
2185 • It may be an odd place to allow comments, but "s//"" # hello/e" has
2187 always worked, unless there happens to be a null character before
2188 the first #. Now it works even in the presence of nulls.
2189 • An invalid range in "tr///" or "y///" no longer results in a memory
2191 leak.
2192 • String eval no longer treats a semicolon-delimited quote-like
2194 operator at the very end ("eval 'q;;'") as a syntax error.
2195 • "warn {$_ => 1} + 1" is no longer a syntax error. The parser used
2197 to get confused with certain list operators followed by an
2198 anonymous hash and then an infix operator that shares its form with
2199 a unary operator.
2200 • "(caller $n)[6]" (which gives the text of the eval) used to return
2202 the actual parser buffer. Modifying it could result in crashes.
2203 Now it always returns a copy. The string returned no longer has
2204 "\n;" tacked on to the end. The returned text also includes here-
2205 doc bodies, which used to be omitted.
2206 • The UTF-8 position cache is now reset when accessing magical
2208 variables, to avoid the string buffer and the UTF-8 position cache
2209 getting out of sync [perl #114410].
2210 • Various cases of get magic being called twice for magical UTF-8
2212 strings have been fixed.
2213 • This code (when not in the presence of $& etc)
2215 $_ = 'x' x 1_000_000;
2217 1 while /(.)/;
2218 used to skip the buffer copy for performance reasons, but suffered
2220 from $1 etc changing if the original string changed. That's now
2221 been fixed.
2222 • Perl doesn't use PerlIO anymore to report out of memory messages,
2224 as PerlIO might attempt to allocate more memory.
2225 • In a regular expression, if something is quantified with "{n,m}"
2227 where "n > m", it can't possibly match. Previously this was a
2228 fatal error, but now is merely a warning (and that something won't
2229 match). [perl #82954].
2230 • It used to be possible for formats defined in subroutines that have
2232 subsequently been undefined and redefined to close over variables
2233 in the wrong pad (the newly-defined enclosing sub), resulting in
2234 crashes or "Bizarre copy" errors.
2235 • Redefinition of XSUBs at run time could produce warnings with the
2237 wrong line number.
2238 • The %vd sprintf format does not support version objects for alpha
2240 versions. It used to output the format itself (%vd) when passed an
2241 alpha version, and also emit an "Invalid conversion in printf"
2242 warning. It no longer does, but produces the empty string in the
2243 output. It also no longer leaks memory in this case.
2244 • "$obj->SUPER::method" calls in the main package could fail if the
2246 SUPER package had already been accessed by other means.
2247 • Stash aliasing ("*foo:: = *bar::") no longer causes SUPER calls to
2249 ignore changes to methods or @ISA or use the wrong package.
2250 • Method calls on packages whose names end in ::SUPER are no longer
2252 treated as SUPER method calls, resulting in failure to find the
2253 method. Furthermore, defining subroutines in such packages no
2254 longer causes them to be found by SUPER method calls on the
2255 containing package [perl #114924].
2256 • "\w" now matches the code points U+200C (ZERO WIDTH NON-JOINER) and
2258 U+200D (ZERO WIDTH JOINER). "\W" no longer matches these. This
2259 change is because Unicode corrected their definition of what "\w"
2260 should match.
2261 • "dump LABEL" no longer leaks its label.
2263 • Constant folding no longer changes the behaviour of functions like
2265 "stat()" and "truncate()" that can take either filenames or
2266 handles. "stat 1 ? foo : bar" nows treats its argument as a file
2267 name (since it is an arbitrary expression), rather than the handle
2268 "foo".
2269 • "truncate FOO, $len" no longer falls back to treating "FOO" as a
2271 file name if the filehandle has been deleted. This was broken in
2272 Perl v5.16.0.
2273 • Subroutine redefinitions after sub-to-glob and glob-to-glob
2275 assignments no longer cause double frees or panic messages.
2276 • "s///" now turns vstrings into plain strings when performing a
2278 substitution, even if the resulting string is the same ("s/a/a/").
2279 • Prototype mismatch warnings no longer erroneously treat constant
2281 subs as having no prototype when they actually have "".
2282 • Constant subroutines and forward declarations no longer prevent
2284 prototype mismatch warnings from omitting the sub name.
2285 • "undef" on a subroutine now clears call checkers.
2287 • The "ref" operator started leaking memory on blessed objects in
2289 Perl v5.16.0. This has been fixed [perl #114340].
2290 • "use" no longer tries to parse its arguments as a statement, making
2292 "use constant { () };" a syntax error [perl #114222].
2293 • On debugging builds, "uninitialized" warnings inside formats no
2295 longer cause assertion failures.
2296 • On debugging builds, subroutines nested inside formats no longer
2298 cause assertion failures [perl #78550].
2299 • Formats and "use" statements are now permitted inside formats.
2301 • "print $x" and "sub { print $x }->()" now always produce the same
2303 output. It was possible for the latter to refuse to close over $x
2304 if the variable was not active; e.g., if it was defined outside a
2305 currently-running named subroutine.
2306 • Similarly, "print $x" and "print eval '$x'" now produce the same
2308 output. This also allows "my $x if 0" variables to be seen in the
2309 debugger [perl #114018].
2310 • Formats called recursively no longer stomp on their own lexical
2312 variables, but each recursive call has its own set of lexicals.
2313 • Attempting to free an active format or the handle associated with
2315 it no longer results in a crash.
2316 • Format parsing no longer gets confused by braces, semicolons and
2318 low-precedence operators. It used to be possible to use braces as
2319 format delimiters (instead of "=" and "."), but only sometimes.
2320 Semicolons and low-precedence operators in format argument lines no
2321 longer confuse the parser into ignoring the line's return value.
2322 In format argument lines, braces can now be used for anonymous
2323 hashes, instead of being treated always as "do" blocks.
2324 • Formats can now be nested inside code blocks in regular expressions
2326 and other quoted constructs ("/(?{...})/" and "qq/${...}/") [perl
2327 #114040].
2328 • Formats are no longer created after compilation errors.
2330 • Under debugging builds, the -DA command line option started
2332 crashing in Perl v5.16.0. It has been fixed [perl #114368].
2333 • A potential deadlock scenario involving the premature termination
2335 of a pseudo- forked child in a Windows build with ithreads enabled
2336 has been fixed. This resolves the common problem of the
2337 t/op/fork.t test hanging on Windows [perl #88840].
2338 • The code which generates errors from "require()" could potentially
2340 read one or two bytes before the start of the filename for
2341 filenames less than three bytes long and ending "/\.p?\z/". This
2342 has now been fixed. Note that it could never have happened with
2343 module names given to "use()" or "require()" anyway.
2344 • The handling of pathnames of modules given to "require()" has been
2346 made thread-safe on VMS.
2347 • Non-blocking sockets have been fixed on VMS.
2349 • Pod can now be nested in code inside a quoted construct outside of
2351 a string eval. This used to work only within string evals [perl
2352 #114040].
2353 • "goto ''" now looks for an empty label, producing the "goto must
2355 have label" error message, instead of exiting the program [perl
2356 #111794].
2357 • "goto "\0"" now dies with "Can't find label" instead of "goto must
2359 have label".
2360 • The C function "hv_store" used to result in crashes when used on
2362 "%^H" [perl #111000].
2363 • A call checker attached to a closure prototype via
2365 "cv_set_call_checker" is now copied to closures cloned from it. So
2366 "cv_set_call_checker" now works inside an attribute handler for a
2367 closure.
2368 • Writing to $^N used to have no effect. Now it croaks with
2370 "Modification of a read-only value" by default, but that can be
2371 overridden by a custom regular expression engine, as with $1 [perl
2372 #112184].
2373 • "undef" on a control character glob ("undef *^H") no longer emits
2375 an erroneous warning about ambiguity [perl #112456].
2376 • For efficiency's sake, many operators and built-in functions return
2378 the same scalar each time. Lvalue subroutines and subroutines in
2379 the CORE:: namespace were allowing this implementation detail to
2380 leak through. "print &CORE::uc("a"), &CORE::uc("b")" used to print
2381 "BB". The same thing would happen with an lvalue subroutine
2382 returning the return value of "uc". Now the value is copied in
2383 such cases.
2384 • "method {}" syntax with an empty block or a block returning an
2386 empty list used to crash or use some random value left on the stack
2387 as its invocant. Now it produces an error.
2388 • "vec" now works with extremely large offsets (>2 GB) [perl
2390 #111730].
2391 • Changes to overload settings now take effect immediately, as do
2393 changes to inheritance that affect overloading. They used to take
2394 effect only after "bless".
2395 Objects that were created before a class had any overloading used
2397 to remain non-overloaded even if the class gained overloading
2398 through "use overload" or @ISA changes, and even after "bless".
2399 This has been fixed [perl #112708].
2400 • Classes with overloading can now inherit fallback values.
2402 • Overloading was not respecting a fallback value of 0 if there were
2404 overloaded objects on both sides of an assignment operator like
2405 "+=" [perl #111856].
2406 • "pos" now croaks with hash and array arguments, instead of
2408 producing erroneous warnings.
2409 • "while(each %h)" now implies "while(defined($_ = each %h))", like
2411 "readline" and "readdir".
2412 • Subs in the CORE:: namespace no longer crash after "undef *_" when
2414 called with no argument list (&CORE::time with no parentheses).
2415 • "unpack" no longer produces the "'/' must follow a numeric type in
2417 unpack" error when it is the data that are at fault [perl #60204].
2418 • "join" and "@array" now call FETCH only once on a tied $" [perl
2420 #8931].
2421 • Some subroutine calls generated by compiling core ops affected by a
2423 "CORE::GLOBAL" override had op checking performed twice. The
2424 checking is always idempotent for pure Perl code, but the double
2425 checking can matter when custom call checkers are involved.
2426 • A race condition used to exist around fork that could cause a
2428 signal sent to the parent to be handled by both parent and child.
2429 Signals are now blocked briefly around fork to prevent this from
2430 happening [perl #82580].
2431 • The implementation of code blocks in regular expressions, such as
2433 "(?{})" and "(??{})", has been heavily reworked to eliminate a
2434 whole slew of bugs. The main user-visible changes are:
2435 • Code blocks within patterns are now parsed in the same pass as
2437 the surrounding code; in particular it is no longer necessary
2438 to have balanced braces: this now works:
2439 /(?{ $x='{' })/
2441 This means that this error message is no longer generated:
2443 Sequence (?{...}) not terminated or not {}-balanced in regex
2445 but a new error may be seen:
2447 Sequence (?{...}) not terminated with ')'
2449 In addition, literal code blocks within run-time patterns are
2451 only compiled once, at perl compile-time:
2452 for my $p (...) {
2454 # this 'FOO' block of code is compiled once,
2455 # at the same time as the surrounding 'for' loop
2456 /$p{(?{FOO;})/;
2457 }
2458 • Lexical variables are now sane as regards scope, recursion and
2460 closure behavior. In particular, "/A(?{B})C/" behaves (from a
2461 closure viewpoint) exactly like "/A/ && do { B } && /C/", while
2462 "qr/A(?{B})C/" is like "sub {/A/ && do { B } && /C/}". So this
2463 code now works how you might expect, creating three regexes
2464 that match 0, 1, and 2:
2465 for my $i (0..2) {
2467 push @r, qr/^(??{$i})$/;
2468 }
2469 "1" =~ $r[1]; # matches
2470 • The "use re 'eval'" pragma is now only required for code blocks
2472 defined at runtime; in particular in the following, the text of
2473 the $r pattern is still interpolated into the new pattern and
2474 recompiled, but the individual compiled code-blocks within $r
2475 are reused rather than being recompiled, and "use re 'eval'"
2476 isn't needed any more:
2477 my $r = qr/abc(?{....})def/;
2479 /xyz$r/;
2480 • Flow control operators no longer crash. Each code block runs in
2482 a new dynamic scope, so "next" etc. will not see any enclosing
2483 loops. "return" returns a value from the code block, not from
2484 any enclosing subroutine.
2485 • Perl normally caches the compilation of run-time patterns, and
2487 doesn't recompile if the pattern hasn't changed, but this is
2488 now disabled if required for the correct behavior of closures.
2489 For example:
2490 my $code = '(??{$x})';
2492 for my $x (1..3) {
2493 # recompile to see fresh value of $x each time
2494 $x =~ /$code/;
2495 }
2496 • The "/msix" and "(?msix)" etc. flags are now propagated into
2498 the return value from "(??{})"; this now works:
2499 "AB" =~ /a(??{'b'})/i;
2501 • Warnings and errors will appear to come from the surrounding
2503 code (or for run-time code blocks, from an eval) rather than
2504 from an "re_eval":
2505 use re 'eval'; $c = '(?{ warn "foo" })'; /$c/;
2507 /(?{ warn "foo" })/;
2508 formerly gave:
2510 foo at (re_eval 1) line 1.
2512 foo at (re_eval 2) line 1.
2513 and now gives:
2515 foo at (eval 1) line 1.
2517 foo at /some/prog line 2.
2518 • Perl now can be recompiled to use any Unicode version. In v5.16,
2520 it worked on Unicodes 6.0 and 6.1, but there were various bugs if
2521 earlier releases were used; the older the release the more
2522 problems.
2523 • "vec" no longer produces "uninitialized" warnings in lvalue context
2525 [perl #9423].
2526 • An optimization involving fixed strings in regular expressions
2528 could cause a severe performance penalty in edge cases. This has
2529 been fixed [perl #76546].
2530 • In certain cases, including empty subpatterns within a regular
2532 expression (such as "(?:)" or "(?:|)") could disable some
2533 optimizations. This has been fixed.
2534 • The "Can't find an opnumber" message that "prototype" produces when
2536 passed a string like "CORE::nonexistent_keyword" now passes UTF-8
2537 and embedded NULs through unchanged [perl #97478].
2538 • "prototype" now treats magical variables like $1 the same way as
2540 non-magical variables when checking for the CORE:: prefix, instead
2541 of treating them as subroutine names.
2542 • Under threaded perls, a runtime code block in a regular expression
2544 could corrupt the package name stored in the op tree, resulting in
2545 bad reads in "caller", and possibly crashes [perl #113060].
2546 • Referencing a closure prototype ("\&{$_[1]}" in an attribute
2548 handler for a closure) no longer results in a copy of the
2549 subroutine (or assertion failures on debugging builds).
2550 • "eval '__PACKAGE__'" now returns the right answer on threaded
2552 builds if the current package has been assigned over (as in
2553 "*ThisPackage:: = *ThatPackage::") [perl #78742].
2554 • If a package is deleted by code that it calls, it is possible for
2556 "caller" to see a stack frame belonging to that deleted package.
2557 "caller" could crash if the stash's memory address was reused for a
2558 scalar and a substitution was performed on the same scalar [perl
2559 #113486].
2560 • "UNIVERSAL::can" no longer treats its first argument differently
2562 depending on whether it is a string or number internally.
2563 • "open" with "<&" for the mode checks to see whether the third
2565 argument is a number, in determining whether to treat it as a file
2566 descriptor or a handle name. Magical variables like $1 were always
2567 failing the numeric check and being treated as handle names.
2568 • "warn"'s handling of magical variables ($1, ties) has undergone
2570 several fixes. "FETCH" is only called once now on a tied argument
2571 or a tied $@ [perl #97480]. Tied variables returning objects that
2572 stringify as "" are no longer ignored. A tied $@ that happened to
2573 return a reference the previous time it was used is no longer
2574 ignored.
2575 • "warn """ now treats $@ with a number in it the same way,
2577 regardless of whether it happened via "$@=3" or "$@="3"". It used
2578 to ignore the former. Now it appends "\t...caught", as it has
2579 always done with "$@="3"".
2580 • Numeric operators on magical variables (e.g., "$1 + 1") used to use
2582 floating point operations even where integer operations were more
2583 appropriate, resulting in loss of accuracy on 64-bit platforms
2584 [perl #109542].
2585 • Unary negation no longer treats a string as a number if the string
2587 happened to be used as a number at some point. So, if $x contains
2588 the string "dogs", "-$x" returns "-dogs" even if "$y=0+$x" has
2589 happened at some point.
2590 • In Perl v5.14, "-'-10'" was fixed to return "10", not "+10". But
2592 magical variables ($1, ties) were not fixed till now [perl #57706].
2593 • Unary negation now treats strings consistently, regardless of the
2595 internal "UTF8" flag.
2596 • A regression introduced in Perl v5.16.0 involving
2598 "tr/SEARCHLIST/REPLACEMENTLIST/" has been fixed. Only the first
2599 instance is supposed to be meaningful if a character appears more
2600 than once in "SEARCHLIST". Under some circumstances, the final
2601 instance was overriding all earlier ones. [perl #113584]
2602 • Regular expressions like "qr/\87/" previously silently inserted a
2604 NUL character, thus matching as if it had been written
2605 "qr/\00087/". Now it matches as if it had been written as
2606 "qr/87/", with a message that the sequence "\8" is unrecognized.
2607 • "__SUB__" now works in special blocks ("BEGIN", "END", etc.).
2609 • Thread creation on Windows could theoretically result in a crash if
2611 done inside a "BEGIN" block. It still does not work properly, but
2612 it no longer crashes [perl #111610].
2613 • "\&{''}" (with the empty string) now autovivifies a stub like any
2615 other sub name, and no longer produces the "Unable to create sub"
2616 error [perl #94476].
2617 • A regression introduced in v5.14.0 has been fixed, in which some
2619 calls to the "re" module would clobber $_ [perl #113750].
2620 • "do FILE" now always either sets or clears $@, even when the file
2622 can't be read. This ensures that testing $@ first (as recommended
2623 by the documentation) always returns the correct result.
2624 • The array iterator used for the "each @array" construct is now
2626 correctly reset when @array is cleared [perl #75596]. This happens,
2627 for example, when the array is globally assigned to, as in "@array
2628 = (...)", but not when its values are assigned to. In terms of the
2629 XS API, it means that "av_clear()" will now reset the iterator.
2630 This mirrors the behaviour of the hash iterator when the hash is
2632 cleared.
2633 • "$class->can", "$class->isa", and "$class->DOES" now return correct
2635 results, regardless of whether that package referred to by $class
2636 exists [perl #47113].
2637 • Arriving signals no longer clear $@ [perl #45173].
2639 • Allow "my ()" declarations with an empty variable list [perl
2641 #113554].
2642 • During parsing, subs declared after errors no longer leave stubs
2644 [perl #113712].
2645 • Closures containing no string evals no longer hang on to their
2647 containing subroutines, allowing variables closed over by outer
2648 subroutines to be freed when the outer sub is freed, even if the
2649 inner sub still exists [perl #89544].
2650 • Duplication of in-memory filehandles by opening with a "<&=" or
2652 ">&=" mode stopped working properly in v5.16.0. It was causing the
2653 new handle to reference a different scalar variable. This has been
2654 fixed [perl #113764].
2655 • "qr//" expressions no longer crash with custom regular expression
2657 engines that do not set "offs" at regular expression compilation
2658 time [perl #112962].
2659 • "delete local" no longer crashes with certain magical arrays and
2661 hashes [perl #112966].
2662 • "local" on elements of certain magical arrays and hashes used not
2664 to arrange to have the element deleted on scope exit, even if the
2665 element did not exist before "local".
2666 • "scalar(write)" no longer returns multiple items [perl #73690].
2668 • String to floating point conversions no longer misparse certain
2670 strings under "use locale" [perl #109318].
2671 • @INC filters that die no longer leak memory [perl #92252].
2673 • The implementations of overloaded operations are now called in the
2675 correct context. This allows, among other things, being able to
2676 properly override "<>" [perl #47119].
2677 • Specifying only the "fallback" key when calling "use overload" now
2679 behaves properly [perl #113010].
2680 • "sub foo { my $a = 0; while ($a) { ... } }" and "sub foo { while
2682 (0) { ... } }" now return the same thing [perl #73618].
2683 • String negation now behaves the same under "use integer;" as it
2685 does without [perl #113012].
2686 • "chr" now returns the Unicode replacement character (U+FFFD) for
2688 -1, regardless of the internal representation. -1 used to wrap if
2689 the argument was tied or a string internally.
2690 • Using a "format" after its enclosing sub was freed could crash as
2692 of perl v5.12.0, if the format referenced lexical variables from
2693 the outer sub.
2694 • Using a "format" after its enclosing sub was undefined could crash
2696 as of perl v5.10.0, if the format referenced lexical variables from
2697 the outer sub.
2698 • Using a "format" defined inside a closure, which format references
2700 lexical variables from outside, never really worked unless the
2701 "write" call was directly inside the closure. In v5.10.0 it even
2702 started crashing. Now the copy of that closure nearest the top of
2703 the call stack is used to find those variables.
2704 • Formats that close over variables in special blocks no longer crash
2706 if a stub exists with the same name as the special block before the
2707 special block is compiled.
2708 • The parser no longer gets confused, treating "eval foo ()" as a
2710 syntax error if preceded by "print;" [perl #16249].
2711 • The return value of "syscall" is no longer truncated on 64-bit
2713 platforms [perl #113980].
2714 • Constant folding no longer causes "print 1 ? FOO : BAR" to print to
2716 the FOO handle [perl #78064].
2717 • "do subname" now calls the named subroutine and uses the file name
2719 it returns, instead of opening a file named "subname".
2720 • Subroutines looked up by rv2cv check hooks (registered by XS
2722 modules) are now taken into consideration when determining whether
2723 "foo bar" should be the sub call "foo(bar)" or the method call
2724 ""bar"->foo".
2725 • "CORE::foo::bar" is no longer treated specially, allowing global
2727 overrides to be called directly via "CORE::GLOBAL::uc(...)" [perl
2728 #113016].
2729 • Calling an undefined sub whose typeglob has been undefined now
2731 produces the customary "Undefined subroutine called" error, instead
2732 of "Not a CODE reference".
2733 • Two bugs involving @ISA have been fixed. "*ISA =
2735 *glob_without_array" and "undef *ISA; @{*ISA}" would prevent future
2736 modifications to @ISA from updating the internal caches used to
2737 look up methods. The *glob_without_array case was a regression
2738 from Perl v5.12.
2739 • Regular expression optimisations sometimes caused "$" with "/m" to
2741 produce failed or incorrect matches [perl #114068].
2742 • "__SUB__" now works in a "sort" block when the enclosing subroutine
2744 is predeclared with "sub foo;" syntax [perl #113710].
2745 • Unicode properties only apply to Unicode code points, which leads
2747 to some subtleties when regular expressions are matched against
2748 above-Unicode code points. There is a warning generated to draw
2749 your attention to this. However, this warning was being generated
2750 inappropriately in some cases, such as when a program was being
2751 parsed. Non-Unicode matches such as "\w" and "[:word:]" should not
2752 generate the warning, as their definitions don't limit them to
2753 apply to only Unicode code points. Now the message is only
2754 generated when matching against "\p{}" and "\P{}". There remains a
2755 bug, [perl #114148], for the very few properties in Unicode that
2756 match just a single code point. The warning is not generated if
2757 they are matched against an above-Unicode code point.
2758 • Uninitialized warnings mentioning hash elements would only mention
2760 the element name if it was not in the first bucket of the hash, due
2761 to an off-by-one error.
2762 • A regular expression optimizer bug could cause multiline "^" to
2764 behave incorrectly in the presence of line breaks, such that
2765 ""/\n\n" =~ m#\A(?:^/$)#im" would not match [perl #115242].
2766 • Failed "fork" in list context no longer corrupts the stack. "@a =
2768 (1, 2, fork, 3)" used to gobble up the 2 and assign "(1, undef, 3)"
2769 if the "fork" call failed.
2770 • Numerous memory leaks have been fixed, mostly involving tied
2772 variables that die, regular expression character classes and code
2773 blocks, and syntax errors.
2774 • Assigning a regular expression ("${qr//}") to a variable that
2776 happens to hold a floating point number no longer causes assertion
2777 failures on debugging builds.
2778 • Assigning a regular expression to a scalar containing a number no
2780 longer causes subsequent numification to produce random numbers.
2781 • Assigning a regular expression to a magic variable no longer wipes
2783 away the magic. This was a regression from v5.10.
2784 • Assigning a regular expression to a blessed scalar no longer
2786 results in crashes. This was also a regression from v5.10.
2787 • Regular expression can now be assigned to tied hash and array
2789 elements with flattening into strings.
2790 • Numifying a regular expression no longer results in an
2792 uninitialized warning.
2793 • Negative array indices no longer cause EXISTS methods of tied
2795 variables to be ignored. This was a regression from v5.12.
2796 • Negative array indices no longer result in crashes on arrays tied
2798 to non-objects.
2799 • "$byte_overload .= $utf8" no longer results in doubly-encoded UTF-8
2801 if the left-hand scalar happened to have produced a UTF-8 string
2802 the last time overloading was invoked.
2803 • "goto &sub" now uses the current value of @_, instead of using the
2805 array the subroutine was originally called with. This means "local
2806 @_ = (...); goto &sub" now works [perl #43077].
2807 • If a debugger is invoked recursively, it no longer stomps on its
2809 own lexical variables. Formerly under recursion all calls would
2810 share the same set of lexical variables [perl #115742].
2811 • *_{ARRAY} returned from a subroutine no longer spontaneously
2813 becomes empty.
2814 • When using "say" to print to a tied filehandle, the value of "$\"
2816 is correctly localized, even if it was previously undef. [perl
2817 #119927]
2818
2820 • UTF8-flagged strings in %ENV on HP-UX 11.00 are buggy
2821 The interaction of UTF8-flagged strings and %ENV on HP-UX 11.00 is
2823 currently dodgy in some not-yet-fully-diagnosed way. Expect test
2824 failures in t/op/magic.t, followed by unknown behavior when storing
2825 wide characters in the environment.
2826
2828 Hojung Yoon (AMORETTE), 24, of Seoul, South Korea, went to his long
2829 rest on May 8, 2013 with llama figurine and autographed TIMTOADY card.
2830 He was a brilliant young Perl 5 & 6 hacker and a devoted member of
2831 Seoul.pm. He programmed Perl, talked Perl, ate Perl, and loved Perl.
2832 We believe that he is still programming in Perl with his broken IBM
2833 laptop somewhere. He will be missed.
2834
2836 Perl v5.18.0 represents approximately 12 months of development since
2837 Perl v5.16.0 and contains approximately 400,000 lines of changes across
2838 2,100 files from 113 authors.
2839 Perl continues to flourish into its third decade thanks to a vibrant
2841 community of users and developers. The following people are known to
2842 have contributed the improvements that became Perl v5.18.0:
2843 Aaron Crane, Aaron Trevena, Abhijit Menon-Sen, Adrian M. Enache, Alan
2845 Haggai Alavi, Alexandr Ciornii, Andrew Tam, Andy Dougherty, Anton
2846 Nikishaev, Aristotle Pagaltzis, Augustina Blair, Bob Ernst, Brad
2847 Gilbert, Breno G. de Oliveira, Brian Carlson, Brian Fraser, Charlie
2848 Gonzalez, Chip Salzenberg, Chris 'BinGOs' Williams, Christian Hansen,
2849 Colin Kuskie, Craig A. Berry, Dagfinn Ilmari Mannsaaker, Daniel Dragan,
2850 Daniel Perrett, Darin McBride, Dave Rolsky, David Golden, David
2851 Leadbeater, David Mitchell, David Nicol, Dominic Hargreaves, E.
2852 Choroba, Eric Brine, Evan Miller, Father Chrysostomos, Florian Ragwitz,
2853 Francois Perrad, George Greer, Goro Fuji, H.Merijn Brand, Herbert
2854 Breunung, Hugo van der Sanden, Igor Zaytsev, James E Keenan, Jan
2855 Dubois, Jasmine Ahuja, Jerry D. Hedden, Jess Robinson, Jesse Luehrs,
2856 Joaquin Ferrero, Joel Berger, John Goodyear, John Peacock, Karen
2857 Etheridge, Karl Williamson, Karthik Rajagopalan, Kent Fredric, Leon
2858 Timmermans, Lucas Holt, Lukas Mai, Marcus Holland-Moritz, Markus
2859 Jansen, Martin Hasch, Matthew Horsfall, Max Maischein, Michael G
2860 Schwern, Michael Schroeder, Moritz Lenz, Nicholas Clark, Niko Tyni,
2861 Oleg Nesterov, Patrik Haegglund, Paul Green, Paul Johnson, Paul
2862 Marquess, Peter Martini, Rafael Garcia-Suarez, Reini Urban, Renee
2863 Baecker, Rhesa Rozendaal, Ricardo Signes, Robin Barker, Ronald J.
2864 Kimball, Ruslan Zakirov, Salvador Fandin~o, Sawyer X, Scott Lanning,
2865 Sergey Alekseev, Shawn M Moore, Shirakata Kentaro, Shlomi Fish,
2866 Sisyphus, Smylers, Steffen Mueller, Steve Hay, Steve Peters, Steven
2867 Schubiger, Sullivan Beck, Sven Strickroth, Sebastien Aperghis-Tramoni,
2868 Thomas Sibley, Tobias Leich, Tom Wyant, Tony Cook, Vadim Konovalov,
2869 Vincent Pit, Volker Schatz, Walt Mankowski, Yves Orton, Zefram.
2870 The list above is almost certainly incomplete as it is automatically
2872 generated from version control history. In particular, it does not
2873 include the names of the (very much appreciated) contributors who
2874 reported issues to the Perl bug tracker.
2875 Many of the changes included in this version originated in the CPAN
2877 modules included in Perl's core. We're grateful to the entire CPAN
2878 community for helping Perl to flourish.
2879 For a more complete list of all of Perl's historical contributors,
2881 please see the AUTHORS file in the Perl source distribution.
2882
2884 If you find what you think is a bug, you might check the articles
2885 recently posted to the comp.lang.perl.misc newsgroup and the perl bug
2886 database at http://rt.perl.org/perlbug/ . There may also be
2887 information at http://www.perl.org/ , the Perl Home Page.
2888 If you believe you have an unreported bug, please run the perlbug
2890 program included with your release. Be sure to trim your bug down to a
2891 tiny but sufficient test case. Your bug report, along with the output
2892 of "perl -V", will be sent off to perlbug@perl.org to be analysed by
2893 the Perl porting team.
2894 If the bug you are reporting has security implications, which make it
2896 inappropriate to send to a publicly archived mailing list, then please
2897 send it to perl5-security-report@perl.org. This points to a closed
2898 subscription unarchived mailing list, which includes all the core
2899 committers, who will be able to help assess the impact of issues,
2900 figure out a resolution, and help co-ordinate the release of patches to
2901 mitigate or fix the problem across all platforms on which Perl is
2902 supported. Please only use this address for security issues in the
2903 Perl core, not for modules independently distributed on CPAN.
2904
2906 The Changes file for an explanation of how to view exhaustive details
2907 on what changed.
2908 The INSTALL file for how to build Perl.
2910 The README file for general stuff.
2912 The Artistic and Copying files for copyright information.
2914perl v5.36.3 2023-11-30 PERL5180DELTA(1)