1PERL5100DELTA(1) Perl Programmers Reference Guide PERL5100DELTA(1)
2
6 perl5100delta - what is new for perl 5.10.0
7
9 This document describes the differences between the 5.8.8 release and
10 the 5.10.0 release.
11 Many of the bug fixes in 5.10.0 were already seen in the 5.8.X
13 maintenance releases; they are not duplicated here and are documented
14 in the set of man pages named perl58[1-8]?delta.
15
17 The "feature" pragma
18 The "feature" pragma is used to enable new syntax that would break
19 Perl's backwards-compatibility with older releases of the language.
20 It's a lexical pragma, like "strict" or "warnings".
21 Currently the following new features are available: "switch" (adds a
23 switch statement), "say" (adds a "say" built-in function), and "state"
24 (adds a "state" keyword for declaring "static" variables). Those
25 features are described in their own sections of this document.
26 The "feature" pragma is also implicitly loaded when you require a
28 minimal perl version (with the "use VERSION" construct) greater than,
29 or equal to, 5.9.5. See feature for details.
30 New -E command-line switch
32 -E is equivalent to -e, but it implicitly enables all optional features
33 (like "use feature ":5.10"").
34 Defined-or operator
36 A new operator "//" (defined-or) has been implemented. The following
37 expression:
38 $a // $b
40 is merely equivalent to
42 defined $a ? $a : $b
44 and the statement
46 $c //= $d;
48 can now be used instead of
50 $c = $d unless defined $c;
52 The "//" operator has the same precedence and associativity as "||".
54 Special care has been taken to ensure that this operator Do What You
55 Mean while not breaking old code, but some edge cases involving the
56 empty regular expression may now parse differently. See perlop for
57 details.
58 Switch and Smart Match operator
60 Perl 5 now has a switch statement. It's available when "use feature
61 'switch'" is in effect. This feature introduces three new keywords,
62 "given", "when", and "default":
63 given ($foo) {
65 when (/^abc/) { $abc = 1; }
66 when (/^def/) { $def = 1; }
67 when (/^xyz/) { $xyz = 1; }
68 default { $nothing = 1; }
69 }
70 A more complete description of how Perl matches the switch variable
72 against the "when" conditions is given in "Switch statements" in
73 perlsyn.
74 This kind of match is called smart match, and it's also possible to use
76 it outside of switch statements, via the new "~~" operator. See "Smart
77 matching in detail" in perlsyn.
78 This feature was contributed by Robin Houston.
80 Regular expressions
82 Recursive Patterns
83 It is now possible to write recursive patterns without using the
84 "(??{})" construct. This new way is more efficient, and in many
85 cases easier to read.
86 Each capturing parenthesis can now be treated as an independent
88 pattern that can be entered by using the "(?PARNO)" syntax ("PARNO"
89 standing for "parenthesis number"). For example, the following
90 pattern will match nested balanced angle brackets:
91 /
93 ^ # start of line
94 ( # start capture buffer 1
95 < # match an opening angle bracket
96 (?: # match one of:
97 (?> # don't backtrack over the inside of this group
98 [^<>]+ # one or more non angle brackets
99 ) # end non backtracking group
100 | # ... or ...
101 (?1) # recurse to bracket 1 and try it again
102 )* # 0 or more times.
103 > # match a closing angle bracket
104 ) # end capture buffer one
105 $ # end of line
106 /x
107 PCRE users should note that Perl's recursive regex feature allows
109 backtracking into a recursed pattern, whereas in PCRE the recursion
110 is atomic or "possessive" in nature. As in the example above, you
111 can add (?>) to control this selectively. (Yves Orton)
112 Named Capture Buffers
114 It is now possible to name capturing parenthesis in a pattern and
115 refer to the captured contents by name. The naming syntax is
116 "(?<NAME>....)". It's possible to backreference to a named buffer
117 with the "\k<NAME>" syntax. In code, the new magical hashes "%+"
118 and "%-" can be used to access the contents of the capture buffers.
119 Thus, to replace all doubled chars with a single copy, one could
121 write
122 s/(?<letter>.)\k<letter>/$+{letter}/g
124 Only buffers with defined contents will be "visible" in the "%+"
126 hash, so it's possible to do something like
127 foreach my $name (keys %+) {
129 print "content of buffer '$name' is $+{$name}\n";
130 }
131 The "%-" hash is a bit more complete, since it will contain array
133 refs holding values from all capture buffers similarly named, if
134 there should be many of them.
135 "%+" and "%-" are implemented as tied hashes through the new module
137 "Tie::Hash::NamedCapture".
138 Users exposed to the .NET regex engine will find that the perl
140 implementation differs in that the numerical ordering of the
141 buffers is sequential, and not "unnamed first, then named". Thus in
142 the pattern
143 /(A)(?<B>B)(C)(?<D>D)/
145 $1 will be 'A', $2 will be 'B', $3 will be 'C' and $4 will be 'D'
147 and not $1 is 'A', $2 is 'C' and $3 is 'B' and $4 is 'D' that a
148 .NET programmer would expect. This is considered a feature. :-)
149 (Yves Orton)
150 Possessive Quantifiers
152 Perl now supports the "possessive quantifier" syntax of the "atomic
153 match" pattern. Basically a possessive quantifier matches as much
154 as it can and never gives any back. Thus it can be used to control
155 backtracking. The syntax is similar to non-greedy matching, except
156 instead of using a '?' as the modifier the '+' is used. Thus "?+",
157 "*+", "++", "{min,max}+" are now legal quantifiers. (Yves Orton)
158 Backtracking control verbs
160 The regex engine now supports a number of special-purpose backtrack
161 control verbs: (*THEN), (*PRUNE), (*MARK), (*SKIP), (*COMMIT),
162 (*FAIL) and (*ACCEPT). See perlre for their descriptions. (Yves
163 Orton)
164 Relative backreferences
166 A new syntax "\g{N}" or "\gN" where "N" is a decimal integer allows
167 a safer form of back-reference notation as well as allowing
168 relative backreferences. This should make it easier to generate and
169 embed patterns that contain backreferences. See "Capture buffers"
170 in perlre. (Yves Orton)
171 "\K" escape
173 The functionality of Jeff Pinyan's module Regexp::Keep has been
174 added to the core. In regular expressions you can now use the
175 special escape "\K" as a way to do something like floating length
176 positive lookbehind. It is also useful in substitutions like:
177 s/(foo)bar/$1/g
179 that can now be converted to
181 s/foo\Kbar//g
183 which is much more efficient. (Yves Orton)
185 Vertical and horizontal whitespace, and linebreak
187 Regular expressions now recognize the "\v" and "\h" escapes that
188 match vertical and horizontal whitespace, respectively. "\V" and
189 "\H" logically match their complements.
190 "\R" matches a generic linebreak, that is, vertical whitespace,
192 plus the multi-character sequence "\x0D\x0A".
193 "say()"
195 say() is a new built-in, only available when "use feature 'say'" is in
196 effect, that is similar to print(), but that implicitly appends a
197 newline to the printed string. See "say" in perlfunc. (Robin Houston)
198 Lexical $_
200 The default variable $_ can now be lexicalized, by declaring it like
201 any other lexical variable, with a simple
202 my $_;
204 The operations that default on $_ will use the lexically-scoped version
206 of $_ when it exists, instead of the global $_.
207 In a "map" or a "grep" block, if $_ was previously my'ed, then the $_
209 inside the block is lexical as well (and scoped to the block).
210 In a scope where $_ has been lexicalized, you can still have access to
212 the global version of $_ by using $::_, or, more simply, by overriding
213 the lexical declaration with "our $_". (Rafael Garcia-Suarez)
214 The "_" prototype
216 A new prototype character has been added. "_" is equivalent to "$" but
217 defaults to $_ if the corresponding argument isn't supplied (both "$"
218 and "_" denote a scalar). Due to the optional nature of the argument,
219 you can only use it at the end of a prototype, or before a semicolon.
220 This has a small incompatible consequence: the prototype() function has
222 been adjusted to return "_" for some built-ins in appropriate cases
223 (for example, "prototype('CORE::rmdir')"). (Rafael Garcia-Suarez)
224 UNITCHECK blocks
226 "UNITCHECK", a new special code block has been introduced, in addition
227 to "BEGIN", "CHECK", "INIT" and "END".
228 "CHECK" and "INIT" blocks, while useful for some specialized purposes,
230 are always executed at the transition between the compilation and the
231 execution of the main program, and thus are useless whenever code is
232 loaded at runtime. On the other hand, "UNITCHECK" blocks are executed
233 just after the unit which defined them has been compiled. See perlmod
234 for more information. (Alex Gough)
235 New Pragma, "mro"
237 A new pragma, "mro" (for Method Resolution Order) has been added. It
238 permits to switch, on a per-class basis, the algorithm that perl uses
239 to find inherited methods in case of a multiple inheritance hierarchy.
240 The default MRO hasn't changed (DFS, for Depth First Search). Another
241 MRO is available: the C3 algorithm. See mro for more information.
242 (Brandon Black)
243 Note that, due to changes in the implementation of class hierarchy
245 search, code that used to undef the *ISA glob will most probably break.
246 Anyway, undef'ing *ISA had the side-effect of removing the magic on the
247 @ISA array and should not have been done in the first place. Also, the
248 cache *::ISA::CACHE:: no longer exists; to force reset the @ISA cache,
249 you now need to use the "mro" API, or more simply to assign to @ISA
250 (e.g. with "@ISA = @ISA").
251 readdir() may return a "short filename" on Windows
253 The readdir() function may return a "short filename" when the long
254 filename contains characters outside the ANSI codepage. Similarly
255 Cwd::cwd() may return a short directory name, and glob() may return
256 short names as well. On the NTFS file system these short names can
257 always be represented in the ANSI codepage. This will not be true for
258 all other file system drivers; e.g. the FAT filesystem stores short
259 filenames in the OEM codepage, so some files on FAT volumes remain
260 unaccessible through the ANSI APIs.
261 Similarly, $^X, @INC, and $ENV{PATH} are preprocessed at startup to
263 make sure all paths are valid in the ANSI codepage (if possible).
264 The Win32::GetLongPathName() function now returns the UTF-8 encoded
266 correct long file name instead of using replacement characters to force
267 the name into the ANSI codepage. The new Win32::GetANSIPathName()
268 function can be used to turn a long pathname into a short one only if
269 the long one cannot be represented in the ANSI codepage.
270 Many other functions in the "Win32" module have been improved to accept
272 UTF-8 encoded arguments. Please see Win32 for details.
273 readpipe() is now overridable
275 The built-in function readpipe() is now overridable. Overriding it
276 permits also to override its operator counterpart, "qx//" (a.k.a.
277 "``"). Moreover, it now defaults to $_ if no argument is provided.
278 (Rafael Garcia-Suarez)
279 Default argument for readline()
281 readline() now defaults to *ARGV if no argument is provided. (Rafael
282 Garcia-Suarez)
283 state() variables
285 A new class of variables has been introduced. State variables are
286 similar to "my" variables, but are declared with the "state" keyword in
287 place of "my". They're visible only in their lexical scope, but their
288 value is persistent: unlike "my" variables, they're not undefined at
289 scope entry, but retain their previous value. (Rafael Garcia-Suarez,
290 Nicholas Clark)
291 To use state variables, one needs to enable them by using
293 use feature 'state';
295 or by using the "-E" command-line switch in one-liners. See
297 "Persistent Private Variables" in perlsub.
298 Stacked filetest operators
300 As a new form of syntactic sugar, it's now possible to stack up
301 filetest operators. You can now write "-f -w -x $file" in a row to mean
302 "-x $file && -w _ && -f _". See "-X" in perlfunc.
303 UNIVERSAL::DOES()
305 The "UNIVERSAL" class has a new method, "DOES()". It has been added to
306 solve semantic problems with the "isa()" method. "isa()" checks for
307 inheritance, while "DOES()" has been designed to be overridden when
308 module authors use other types of relations between classes (in
309 addition to inheritance). (chromatic)
310 See "$obj->DOES( ROLE )" in UNIVERSAL.
312 Formats
314 Formats were improved in several ways. A new field, "^*", can be used
315 for variable-width, one-line-at-a-time text. Null characters are now
316 handled correctly in picture lines. Using "@#" and "~~" together will
317 now produce a compile-time error, as those format fields are
318 incompatible. perlform has been improved, and miscellaneous bugs
319 fixed.
320 Byte-order modifiers for pack() and unpack()
322 There are two new byte-order modifiers, ">" (big-endian) and "<"
323 (little-endian), that can be appended to most pack() and unpack()
324 template characters and groups to force a certain byte-order for that
325 type or group. See "pack" in perlfunc and perlpacktut for details.
326 "no VERSION"
328 You can now use "no" followed by a version number to specify that you
329 want to use a version of perl older than the specified one.
330 "chdir", "chmod" and "chown" on filehandles
332 "chdir", "chmod" and "chown" can now work on filehandles as well as
333 filenames, if the system supports respectively "fchdir", "fchmod" and
334 "fchown", thanks to a patch provided by Gisle Aas.
335 OS groups
337 $( and $) now return groups in the order where the OS returns them,
338 thanks to Gisle Aas. This wasn't previously the case.
339 Recursive sort subs
341 You can now use recursive subroutines with sort(), thanks to Robin
342 Houston.
343 Exceptions in constant folding
345 The constant folding routine is now wrapped in an exception handler,
346 and if folding throws an exception (such as attempting to evaluate
347 0/0), perl now retains the current optree, rather than aborting the
348 whole program. Without this change, programs would not compile if they
349 had expressions that happened to generate exceptions, even though those
350 expressions were in code that could never be reached at runtime.
351 (Nicholas Clark, Dave Mitchell)
352 Source filters in @INC
354 It's possible to enhance the mechanism of subroutine hooks in @INC by
355 adding a source filter on top of the filehandle opened and returned by
356 the hook. This feature was planned a long time ago, but wasn't quite
357 working until now. See "require" in perlfunc for details. (Nicholas
358 Clark)
359 New internal variables
361 "${^RE_DEBUG_FLAGS}"
362 This variable controls what debug flags are in effect for the
363 regular expression engine when running under "use re "debug"". See
364 re for details.
365 "${^CHILD_ERROR_NATIVE}"
367 This variable gives the native status returned by the last pipe
368 close, backtick command, successful call to wait() or waitpid(), or
369 from the system() operator. See perlvar for details. (Contributed
370 by Gisle Aas.)
371 "${^RE_TRIE_MAXBUF}"
373 See "Trie optimisation of literal string alternations".
374 "${^WIN32_SLOPPY_STAT}"
376 See "Sloppy stat on Windows".
377 Miscellaneous
379 "unpack()" now defaults to unpacking the $_ variable.
380 "mkdir()" without arguments now defaults to $_.
382 The internal dump output has been improved, so that non-printable
384 characters such as newline and backspace are output in "\x" notation,
385 rather than octal.
386 The -C option can no longer be used on the "#!" line. It wasn't working
388 there anyway, since the standard streams are already set up at this
389 point in the execution of the perl interpreter. You can use binmode()
390 instead to get the desired behaviour.
391 UCD 5.0.0
393 The copy of the Unicode Character Database included in Perl 5 has been
394 updated to version 5.0.0.
395 MAD
397 MAD, which stands for Miscellaneous Attribute Decoration, is a still-
398 in-development work leading to a Perl 5 to Perl 6 converter. To enable
399 it, it's necessary to pass the argument "-Dmad" to Configure. The
400 obtained perl isn't binary compatible with a regular perl 5.10, and has
401 space and speed penalties; moreover not all regression tests still pass
402 with it. (Larry Wall, Nicholas Clark)
403 kill() on Windows
405 On Windows platforms, "kill(-9, $pid)" now kills a process tree. (On
406 Unix, this delivers the signal to all processes in the same process
407 group.)
408
410 Packing and UTF-8 strings
411 The semantics of pack() and unpack() regarding UTF-8-encoded data has
412 been changed. Processing is now by default character per character
413 instead of byte per byte on the underlying encoding. Notably, code that
414 used things like "pack("a*", $string)" to see through the encoding of
415 string will now simply get back the original $string. Packed strings
416 can also get upgraded during processing when you store upgraded
417 characters. You can get the old behaviour by using "use bytes".
418 To be consistent with pack(), the "C0" in unpack() templates indicates
420 that the data is to be processed in character mode, i.e. character by
421 character; on the contrary, "U0" in unpack() indicates UTF-8 mode,
422 where the packed string is processed in its UTF-8-encoded Unicode form
423 on a byte by byte basis. This is reversed with regard to perl 5.8.X,
424 but now consistent between pack() and unpack().
425 Moreover, "C0" and "U0" can also be used in pack() templates to specify
427 respectively character and byte modes.
428 "C0" and "U0" in the middle of a pack or unpack format now switch to
430 the specified encoding mode, honoring parens grouping. Previously,
431 parens were ignored.
432 Also, there is a new pack() character format, "W", which is intended to
434 replace the old "C". "C" is kept for unsigned chars coded as bytes in
435 the strings internal representation. "W" represents unsigned (logical)
436 character values, which can be greater than 255. It is therefore more
437 robust when dealing with potentially UTF-8-encoded data (as "C" will
438 wrap values outside the range 0..255, and not respect the string
439 encoding).
440 In practice, that means that pack formats are now encoding-neutral,
442 except "C".
443 For consistency, "A" in unpack() format now trims all Unicode
445 whitespace from the end of the string. Before perl 5.9.2, it used to
446 strip only the classical ASCII space characters.
447 Byte/character count feature in unpack()
449 A new unpack() template character, ".", returns the number of bytes or
450 characters (depending on the selected encoding mode, see above) read so
451 far.
452 The $* and $# variables have been removed
454 $*, which was deprecated in favor of the "/s" and "/m" regexp
455 modifiers, has been removed.
456 The deprecated $# variable (output format for numbers) has been
458 removed.
459 Two new severe warnings, "$#/$* is no longer supported", have been
461 added.
462 substr() lvalues are no longer fixed-length
464 The lvalues returned by the three argument form of substr() used to be
465 a "fixed length window" on the original string. In some cases this
466 could cause surprising action at distance or other undefined behaviour.
467 Now the length of the window adjusts itself to the length of the string
468 assigned to it.
469 Parsing of "-f _"
471 The identifier "_" is now forced to be a bareword after a filetest
472 operator. This solves a number of misparsing issues when a global "_"
473 subroutine is defined.
474 ":unique"
476 The ":unique" attribute has been made a no-op, since its current
477 implementation was fundamentally flawed and not threadsafe.
478 Effect of pragmas in eval
480 The compile-time value of the "%^H" hint variable can now propagate
481 into eval("")uated code. This makes it more useful to implement lexical
482 pragmas.
483 As a side-effect of this, the overloaded-ness of constants now
485 propagates into eval("").
486 chdir FOO
488 A bareword argument to chdir() is now recognized as a file handle.
489 Earlier releases interpreted the bareword as a directory name. (Gisle
490 Aas)
491 Handling of .pmc files
493 An old feature of perl was that before "require" or "use" look for a
494 file with a .pm extension, they will first look for a similar filename
495 with a .pmc extension. If this file is found, it will be loaded in
496 place of any potentially existing file ending in a .pm extension.
497 Previously, .pmc files were loaded only if more recent than the
499 matching .pm file. Starting with 5.9.4, they'll be always loaded if
500 they exist.
501 $^V is now a "version" object instead of a v-string
503 $^V can still be used with the %vd format in printf, but any character-
504 level operations will now access the string representation of the
505 "version" object and not the ordinals of a v-string. Expressions like
506 "substr($^V, 0, 2)" or "split //, $^V" no longer work and must be
507 rewritten.
508 @- and @+ in patterns
510 The special arrays "@-" and "@+" are no longer interpolated in regular
511 expressions. (Sadahiro Tomoyuki)
512 $AUTOLOAD can now be tainted
514 If you call a subroutine by a tainted name, and if it defers to an
515 AUTOLOAD function, then $AUTOLOAD will be (correctly) tainted. (Rick
516 Delaney)
517 Tainting and printf
519 When perl is run under taint mode, "printf()" and "sprintf()" will now
520 reject any tainted format argument. (Rafael Garcia-Suarez)
521 undef and signal handlers
523 Undefining or deleting a signal handler via "undef $SIG{FOO}" is now
524 equivalent to setting it to 'DEFAULT'. (Rafael Garcia-Suarez)
525 strictures and dereferencing in defined()
527 "use strict 'refs'" was ignoring taking a hard reference in an argument
528 to defined(), as in :
529 use strict 'refs';
531 my $x = 'foo';
532 if (defined $$x) {...}
533 This now correctly produces the run-time error "Can't use string as a
535 SCALAR ref while "strict refs" in use".
536 "defined @$foo" and "defined %$bar" are now also subject to "strict
538 'refs'" (that is, $foo and $bar shall be proper references there.)
539 ("defined(@foo)" and "defined(%bar)" are discouraged constructs
540 anyway.) (Nicholas Clark)
541 "(?p{})" has been removed
543 The regular expression construct "(?p{})", which was deprecated in perl
544 5.8, has been removed. Use "(??{})" instead. (Rafael Garcia-Suarez)
545 Pseudo-hashes have been removed
547 Support for pseudo-hashes has been removed from Perl 5.9. (The "fields"
548 pragma remains here, but uses an alternate implementation.)
549 Removal of the bytecode compiler and of perlcc
551 "perlcc", the byteloader and the supporting modules (B::C, B::CC,
552 B::Bytecode, etc.) are no longer distributed with the perl sources.
553 Those experimental tools have never worked reliably, and, due to the
554 lack of volunteers to keep them in line with the perl interpreter
555 developments, it was decided to remove them instead of shipping a
556 broken version of those. The last version of those modules can be
557 found with perl 5.9.4.
558 However the B compiler framework stays supported in the perl core, as
560 with the more useful modules it has permitted (among others, B::Deparse
561 and B::Concise).
562 Removal of the JPL
564 The JPL (Java-Perl Lingo) has been removed from the perl sources
565 tarball.
566 Recursive inheritance detected earlier
568 Perl will now immediately throw an exception if you modify any
569 package's @ISA in such a way that it would cause recursive inheritance.
570 Previously, the exception would not occur until Perl attempted to make
572 use of the recursive inheritance while resolving a method or doing a
573 "$foo->isa($bar)" lookup.
574 warnings::enabled and warnings::warnif changed to favor users of modules
576 The behaviour in 5.10.x favors the person using the module; The
577 behaviour in 5.8.x favors the module writer;
578 Assume the following code:
580 main calls Foo::Bar::baz()
582 Foo::Bar inherits from Foo::Base
583 Foo::Bar::baz() calls Foo::Base::_bazbaz()
584 Foo::Base::_bazbaz() calls: warnings::warnif('substr', 'some warning
585 message');
586 On 5.8.x, the code warns when Foo::Bar contains "use warnings;" It does
588 not matter if Foo::Base or main have warnings enabled to disable the
589 warning one has to modify Foo::Bar.
590 On 5.10.0 and newer, the code warns when main contains "use warnings;"
592 It does not matter if Foo::Base or Foo::Bar have warnings enabled to
593 disable the warning one has to modify main.
594
596 Upgrading individual core modules
597 Even more core modules are now also available separately through the
598 CPAN. If you wish to update one of these modules, you don't need to
599 wait for a new perl release. From within the cpan shell, running the
600 'r' command will report on modules with upgrades available. See
601 "perldoc CPAN" for more information.
602 Pragmata Changes
604 "feature"
605 The new pragma "feature" is used to enable new features that might
606 break old code. See "The "feature" pragma" above.
607 "mro"
609 This new pragma enables to change the algorithm used to resolve
610 inherited methods. See "New Pragma, "mro"" above.
611 Scoping of the "sort" pragma
613 The "sort" pragma is now lexically scoped. Its effect used to be
614 global.
615 Scoping of "bignum", "bigint", "bigrat"
617 The three numeric pragmas "bignum", "bigint" and "bigrat" are now
618 lexically scoped. (Tels)
619 "base"
621 The "base" pragma now warns if a class tries to inherit from
622 itself. (Curtis "Ovid" Poe)
623 "strict" and "warnings"
625 "strict" and "warnings" will now complain loudly if they are loaded
626 via incorrect casing (as in "use Strict;"). (Johan Vromans)
627 "version"
629 The "version" module provides support for version objects.
630 "warnings"
632 The "warnings" pragma doesn't load "Carp" anymore. That means that
633 code that used "Carp" routines without having loaded it at compile
634 time might need to be adjusted; typically, the following (faulty)
635 code won't work anymore, and will require parentheses to be added
636 after the function name:
637 use warnings;
639 require Carp;
640 Carp::confess 'argh';
641 "less"
643 "less" now does something useful (or at least it tries to). In
644 fact, it has been turned into a lexical pragma. So, in your
645 modules, you can now test whether your users have requested to use
646 less CPU, or less memory, less magic, or maybe even less fat. See
647 less for more. (Joshua ben Jore)
648 New modules
650 · "encoding::warnings", by Audrey Tang, is a module to emit warnings
651 whenever an ASCII character string containing high-bit bytes is
652 implicitly converted into UTF-8. It's a lexical pragma since Perl
653 5.9.4; on older perls, its effect is global.
654 · "Module::CoreList", by Richard Clamp, is a small handy module that
656 tells you what versions of core modules ship with any versions of
657 Perl 5. It comes with a command-line frontend, "corelist".
658 · "Math::BigInt::FastCalc" is an XS-enabled, and thus faster, version
660 of "Math::BigInt::Calc".
661 · "Compress::Zlib" is an interface to the zlib compression library.
663 It comes with a bundled version of zlib, so having a working zlib
664 is not a prerequisite to install it. It's used by "Archive::Tar"
665 (see below).
666 · "IO::Zlib" is an "IO::"-style interface to "Compress::Zlib".
668 · "Archive::Tar" is a module to manipulate "tar" archives.
670 · "Digest::SHA" is a module used to calculate many types of SHA
672 digests, has been included for SHA support in the CPAN module.
673 · "ExtUtils::CBuilder" and "ExtUtils::ParseXS" have been added.
675 · "Hash::Util::FieldHash", by Anno Siegel, has been added. This
677 module provides support for field hashes: hashes that maintain an
678 association of a reference with a value, in a thread-safe garbage-
679 collected way. Such hashes are useful to implement inside-out
680 objects.
681 · "Module::Build", by Ken Williams, has been added. It's an
683 alternative to "ExtUtils::MakeMaker" to build and install perl
684 modules.
685 · "Module::Load", by Jos Boumans, has been added. It provides a
687 single interface to load Perl modules and .pl files.
688 · "Module::Loaded", by Jos Boumans, has been added. It's used to mark
690 modules as loaded or unloaded.
691 · "Package::Constants", by Jos Boumans, has been added. It's a simple
693 helper to list all constants declared in a given package.
694 · "Win32API::File", by Tye McQueen, has been added (for Windows
696 builds). This module provides low-level access to Win32 system API
697 calls for files/dirs.
698 · "Locale::Maketext::Simple", needed by CPANPLUS, is a simple wrapper
700 around "Locale::Maketext::Lexicon". Note that
701 "Locale::Maketext::Lexicon" isn't included in the perl core; the
702 behaviour of "Locale::Maketext::Simple" gracefully degrades when
703 the later isn't present.
704 · "Params::Check" implements a generic input parsing/checking
706 mechanism. It is used by CPANPLUS.
707 · "Term::UI" simplifies the task to ask questions at a terminal
709 prompt.
710 · "Object::Accessor" provides an interface to create per-object
712 accessors.
713 · "Module::Pluggable" is a simple framework to create modules that
715 accept pluggable sub-modules.
716 · "Module::Load::Conditional" provides simple ways to query and
718 possibly load installed modules.
719 · "Time::Piece" provides an object oriented interface to time
721 functions, overriding the built-ins localtime() and gmtime().
722 · "IPC::Cmd" helps to find and run external commands, possibly
724 interactively.
725 · "File::Fetch" provide a simple generic file fetching mechanism.
727 · "Log::Message" and "Log::Message::Simple" are used by the log
729 facility of "CPANPLUS".
730 · "Archive::Extract" is a generic archive extraction mechanism for
732 .tar (plain, gzipped or bzipped) or .zip files.
733 · "CPANPLUS" provides an API and a command-line tool to access the
735 CPAN mirrors.
736 · "Pod::Escapes" provides utilities that are useful in decoding Pod
738 E<...> sequences.
739 · "Pod::Simple" is now the backend for several of the Pod-related
741 modules included with Perl.
742 Selected Changes to Core Modules
744 "Attribute::Handlers"
745 "Attribute::Handlers" can now report the caller's file and line
746 number. (David Feldman)
747 All interpreted attributes are now passed as array references.
749 (Damian Conway)
750 "B::Lint"
752 "B::Lint" is now based on "Module::Pluggable", and so can be
753 extended with plugins. (Joshua ben Jore)
754 "B" It's now possible to access the lexical pragma hints ("%^H") by
756 using the method B::COP::hints_hash(). It returns a "B::RHE"
757 object, which in turn can be used to get a hash reference via the
758 method B::RHE::HASH(). (Joshua ben Jore)
759 "Thread"
761 As the old 5005thread threading model has been removed, in favor of
762 the ithreads scheme, the "Thread" module is now a compatibility
763 wrapper, to be used in old code only. It has been removed from the
764 default list of dynamic extensions.
765
767 perl -d
768 The Perl debugger can now save all debugger commands for sourcing
769 later; notably, it can now emulate stepping backwards, by
770 restarting and rerunning all bar the last command from a saved
771 command history.
772 It can also display the parent inheritance tree of a given class,
774 with the "i" command.
775 ptar
777 "ptar" is a pure perl implementation of "tar" that comes with
778 "Archive::Tar".
779 ptardiff
781 "ptardiff" is a small utility used to generate a diff between the
782 contents of a tar archive and a directory tree. Like "ptar", it
783 comes with "Archive::Tar".
784 shasum
786 "shasum" is a command-line utility, used to print or to check SHA
787 digests. It comes with the new "Digest::SHA" module.
788 corelist
790 The "corelist" utility is now installed with perl (see "New
791 modules" above).
792 h2ph and h2xs
794 "h2ph" and "h2xs" have been made more robust with regard to
795 "modern" C code.
796 "h2xs" implements a new option "--use-xsloader" to force use of
798 "XSLoader" even in backwards compatible modules.
799 The handling of authors' names that had apostrophes has been fixed.
801 Any enums with negative values are now skipped.
803 perlivp
805 "perlivp" no longer checks for *.ph files by default. Use the new
806 "-a" option to run all tests.
807 find2perl
809 "find2perl" now assumes "-print" as a default action. Previously,
810 it needed to be specified explicitly.
811 Several bugs have been fixed in "find2perl", regarding "-exec" and
813 "-eval". Also the options "-path", "-ipath" and "-iname" have been
814 added.
815 config_data
817 "config_data" is a new utility that comes with "Module::Build". It
818 provides a command-line interface to the configuration of Perl
819 modules that use Module::Build's framework of configurability (that
820 is, *::ConfigData modules that contain local configuration
821 information for their parent modules.)
822 cpanp
824 "cpanp", the CPANPLUS shell, has been added. ("cpanp-run-perl", a
825 helper for CPANPLUS operation, has been added too, but isn't
826 intended for direct use).
827 cpan2dist
829 "cpan2dist" is a new utility that comes with CPANPLUS. It's a tool
830 to create distributions (or packages) from CPAN modules.
831 pod2html
833 The output of "pod2html" has been enhanced to be more customizable
834 via CSS. Some formatting problems were also corrected. (Jari Aalto)
835
837 The perlpragma manpage documents how to write one's own lexical pragmas
838 in pure Perl (something that is possible starting with 5.9.4).
839 The new perlglossary manpage is a glossary of terms used in the Perl
841 documentation, technical and otherwise, kindly provided by O'Reilly
842 Media, Inc.
843 The perlreguts manpage, courtesy of Yves Orton, describes internals of
845 the Perl regular expression engine.
846 The perlreapi manpage describes the interface to the perl interpreter
848 used to write pluggable regular expression engines (by var Arnfjoerd`
849 Bjarmason).
850 The perlunitut manpage is an tutorial for programming with Unicode and
852 string encodings in Perl, courtesy of Juerd Waalboer.
853 A new manual page, perlunifaq (the Perl Unicode FAQ), has been added
855 (Juerd Waalboer).
856 The perlcommunity manpage gives a description of the Perl community on
858 the Internet and in real life. (Edgar "Trizor" Bering)
859 The CORE manual page documents the "CORE::" namespace. (Tels)
861 The long-existing feature of "/(?{...})/" regexps setting $_ and pos()
863 is now documented.
864
866 In-place sorting
867 Sorting arrays in place ("@a = sort @a") is now optimized to avoid
868 making a temporary copy of the array.
869 Likewise, "reverse sort ..." is now optimized to sort in reverse,
871 avoiding the generation of a temporary intermediate list.
872 Lexical array access
874 Access to elements of lexical arrays via a numeric constant between 0
875 and 255 is now faster. (This used to be only the case for global
876 arrays.)
877 XS-assisted SWASHGET
879 Some pure-perl code that perl was using to retrieve Unicode properties
880 and transliteration mappings has been reimplemented in XS.
881 Constant subroutines
883 The interpreter internals now support a far more memory efficient form
884 of inlineable constants. Storing a reference to a constant value in a
885 symbol table is equivalent to a full typeglob referencing a constant
886 subroutine, but using about 400 bytes less memory. This proxy constant
887 subroutine is automatically upgraded to a real typeglob with subroutine
888 if necessary. The approach taken is analogous to the existing space
889 optimisation for subroutine stub declarations, which are stored as
890 plain scalars in place of the full typeglob.
891 Several of the core modules have been converted to use this feature for
893 their system dependent constants - as a result "use POSIX;" now takes
894 about 200K less memory.
895 "PERL_DONT_CREATE_GVSV"
897 The new compilation flag "PERL_DONT_CREATE_GVSV", introduced as an
898 option in perl 5.8.8, is turned on by default in perl 5.9.3. It
899 prevents perl from creating an empty scalar with every new typeglob.
900 See perl589delta for details.
901 Weak references are cheaper
903 Weak reference creation is now O(1) rather than O(n), courtesy of
904 Nicholas Clark. Weak reference deletion remains O(n), but if deletion
905 only happens at program exit, it may be skipped completely.
906 sort() enhancements
908 Salvador Fandin~o provided improvements to reduce the memory usage of
909 "sort" and to speed up some cases.
910 Memory optimisations
912 Several internal data structures (typeglobs, GVs, CVs, formats) have
913 been restructured to use less memory. (Nicholas Clark)
914 UTF-8 cache optimisation
916 The UTF-8 caching code is now more efficient, and used more often.
917 (Nicholas Clark)
918 Sloppy stat on Windows
920 On Windows, perl's stat() function normally opens the file to determine
921 the link count and update attributes that may have been changed through
922 hard links. Setting ${^WIN32_SLOPPY_STAT} to a true value speeds up
923 stat() by not performing this operation. (Jan Dubois)
924 Regular expressions optimisations
926 Engine de-recursivised
927 The regular expression engine is no longer recursive, meaning that
928 patterns that used to overflow the stack will either die with
929 useful explanations, or run to completion, which, since they were
930 able to blow the stack before, will likely take a very long time to
931 happen. If you were experiencing the occasional stack overflow (or
932 segfault) and upgrade to discover that now perl apparently hangs
933 instead, look for a degenerate regex. (Dave Mitchell)
934 Single char char-classes treated as literals
936 Classes of a single character are now treated the same as if the
937 character had been used as a literal, meaning that code that uses
938 char-classes as an escaping mechanism will see a speedup. (Yves
939 Orton)
940 Trie optimisation of literal string alternations
942 Alternations, where possible, are optimised into more efficient
943 matching structures. String literal alternations are merged into a
944 trie and are matched simultaneously. This means that instead of
945 O(N) time for matching N alternations at a given point, the new
946 code performs in O(1) time. A new special variable,
947 ${^RE_TRIE_MAXBUF}, has been added to fine-tune this optimization.
948 (Yves Orton)
949 Note: Much code exists that works around perl's historic poor
951 performance on alternations. Often the tricks used to do so will
952 disable the new optimisations. Hopefully the utility modules used
953 for this purpose will be educated about these new optimisations.
954 Aho-Corasick start-point optimisation
956 When a pattern starts with a trie-able alternation and there aren't
957 better optimisations available, the regex engine will use Aho-
958 Corasick matching to find the start point. (Yves Orton)
959
961 Configuration improvements
962 "-Dusesitecustomize"
963 Run-time customization of @INC can be enabled by passing the
964 "-Dusesitecustomize" flag to Configure. When enabled, this will
965 make perl run $sitelibexp/sitecustomize.pl before anything else.
966 This script can then be set up to add additional entries to @INC.
967 Relocatable installations
969 There is now Configure support for creating a relocatable perl
970 tree. If you Configure with "-Duserelocatableinc", then the paths
971 in @INC (and everything else in %Config) can be optionally located
972 via the path of the perl executable.
973 That means that, if the string ".../" is found at the start of any
975 path, it's substituted with the directory of $^X. So, the
976 relocation can be configured on a per-directory basis, although the
977 default with "-Duserelocatableinc" is that everything is relocated.
978 The initial install is done to the original configured prefix.
979 strlcat() and strlcpy()
981 The configuration process now detects whether strlcat() and
982 strlcpy() are available. When they are not available, perl's own
983 version is used (from Russ Allbery's public domain implementation).
984 Various places in the perl interpreter now use them. (Steve Peters)
985 "d_pseudofork" and "d_printf_format_null"
987 A new configuration variable, available as $Config{d_pseudofork} in
988 the Config module, has been added, to distinguish real fork()
989 support from fake pseudofork used on Windows platforms.
990 A new configuration variable, "d_printf_format_null", has been
992 added, to see if printf-like formats are allowed to be NULL.
993 Configure help
995 "Configure -h" has been extended with the most commonly used
996 options.
997 Compilation improvements
999 Parallel build
1000 Parallel makes should work properly now, although there may still
1001 be problems if "make test" is instructed to run in parallel.
1002 Borland's compilers support
1004 Building with Borland's compilers on Win32 should work more
1005 smoothly. In particular Steve Hay has worked to side step many
1006 warnings emitted by their compilers and at least one C compiler
1007 internal error.
1008 Static build on Windows
1010 Perl extensions on Windows now can be statically built into the
1011 Perl DLL.
1012 Also, it's now possible to build a "perl-static.exe" that doesn't
1014 depend on the Perl DLL on Win32. See the Win32 makefiles for
1015 details. (Vadim Konovalov)
1016 ppport.h files
1018 All ppport.h files in the XS modules bundled with perl are now
1019 autogenerated at build time. (Marcus Holland-Moritz)
1020 C++ compatibility
1022 Efforts have been made to make perl and the core XS modules
1023 compilable with various C++ compilers (although the situation is
1024 not perfect with some of the compilers on some of the platforms
1025 tested.)
1026 Support for Microsoft 64-bit compiler
1028 Support for building perl with Microsoft's 64-bit compiler has been
1029 improved. (ActiveState)
1030 Visual C++
1032 Perl can now be compiled with Microsoft Visual C++ 2005 (and 2008
1033 Beta 2).
1034 Win32 builds
1036 All win32 builds (MS-Win, WinCE) have been merged and cleaned up.
1037 Installation improvements
1039 Module auxiliary files
1040 README files and changelogs for CPAN modules bundled with perl are
1041 no longer installed.
1042 New Or Improved Platforms
1044 Perl has been reported to work on Symbian OS. See perlsymbian for more
1045 information.
1046 Many improvements have been made towards making Perl work correctly on
1048 z/OS.
1049 Perl has been reported to work on DragonFlyBSD and MidnightBSD.
1051 Perl has also been reported to work on NexentaOS (
1053 http://www.gnusolaris.org/ ).
1054 The VMS port has been improved. See perlvms.
1056 Support for Cray XT4 Catamount/Qk has been added. See
1058 hints/catamount.sh in the source code distribution for more
1059 information.
1060 Vendor patches have been merged for RedHat and Gentoo.
1062 DynaLoader::dl_unload_file() now works on Windows.
1064
1066 strictures in regexp-eval blocks
1067 "strict" wasn't in effect in regexp-eval blocks ("/(?{...})/").
1068 Calling CORE::require()
1070 CORE::require() and CORE::do() were always parsed as require() and
1071 do() when they were overridden. This is now fixed.
1072 Subscripts of slices
1074 You can now use a non-arrowed form for chained subscripts after a
1075 list slice, like in:
1076 ({foo => "bar"})[0]{foo}
1078 This used to be a syntax error; a "->" was required.
1080 "no warnings 'category'" works correctly with -w
1082 Previously when running with warnings enabled globally via "-w",
1083 selective disabling of specific warning categories would actually
1084 turn off all warnings. This is now fixed; now "no warnings 'io';"
1085 will only turn off warnings in the "io" class. Previously it would
1086 erroneously turn off all warnings.
1087 threads improvements
1089 Several memory leaks in ithreads were closed. Also, ithreads were
1090 made less memory-intensive.
1091 "threads" is now a dual-life module, also available on CPAN. It has
1093 been expanded in many ways. A kill() method is available for thread
1094 signalling. One can get thread status, or the list of running or
1095 joinable threads.
1096 A new "threads->exit()" method is used to exit from the application
1098 (this is the default for the main thread) or from the current
1099 thread only (this is the default for all other threads). On the
1100 other hand, the exit() built-in now always causes the whole
1101 application to terminate. (Jerry D. Hedden)
1102 chr() and negative values
1104 chr() on a negative value now gives "\x{FFFD}", the Unicode
1105 replacement character, unless when the "bytes" pragma is in effect,
1106 where the low eight bits of the value are used.
1107 PERL5SHELL and tainting
1109 On Windows, the PERL5SHELL environment variable is now checked for
1110 taintedness. (Rafael Garcia-Suarez)
1111 Using *FILE{IO}
1113 "stat()" and "-X" filetests now treat *FILE{IO} filehandles like
1114 *FILE filehandles. (Steve Peters)
1115 Overloading and reblessing
1117 Overloading now works when references are reblessed into another
1118 class. Internally, this has been implemented by moving the flag
1119 for "overloading" from the reference to the referent, which
1120 logically is where it should always have been. (Nicholas Clark)
1121 Overloading and UTF-8
1123 A few bugs related to UTF-8 handling with objects that have
1124 stringification overloaded have been fixed. (Nicholas Clark)
1125 eval memory leaks fixed
1127 Traditionally, "eval 'syntax error'" has leaked badly. Many (but
1128 not all) of these leaks have now been eliminated or reduced. (Dave
1129 Mitchell)
1130 Random device on Windows
1132 In previous versions, perl would read the file /dev/urandom if it
1133 existed when seeding its random number generator. That file is
1134 unlikely to exist on Windows, and if it did would probably not
1135 contain appropriate data, so perl no longer tries to read it on
1136 Windows. (Alex Davies)
1137 PERLIO_DEBUG
1139 The "PERLIO_DEBUG" environment variable no longer has any effect
1140 for setuid scripts and for scripts run with -T.
1141 Moreover, with a thread-enabled perl, using "PERLIO_DEBUG" could
1143 lead to an internal buffer overflow. This has been fixed.
1144 PerlIO::scalar and read-only scalars
1146 PerlIO::scalar will now prevent writing to read-only scalars.
1147 Moreover, seek() is now supported with PerlIO::scalar-based
1148 filehandles, the underlying string being zero-filled as needed.
1149 (Rafael, Jarkko Hietaniemi)
1150 study() and UTF-8
1152 study() never worked for UTF-8 strings, but could lead to false
1153 results. It's now a no-op on UTF-8 data. (Yves Orton)
1154 Critical signals
1156 The signals SIGILL, SIGBUS and SIGSEGV are now always delivered in
1157 an "unsafe" manner (contrary to other signals, that are deferred
1158 until the perl interpreter reaches a reasonably stable state; see
1159 "Deferred Signals (Safe Signals)" in perlipc). (Rafael)
1160 @INC-hook fix
1162 When a module or a file is loaded through an @INC-hook, and when
1163 this hook has set a filename entry in %INC, __FILE__ is now set for
1164 this module accordingly to the contents of that %INC entry.
1165 (Rafael)
1166 "-t" switch fix
1168 The "-w" and "-t" switches can now be used together without messing
1169 up which categories of warnings are activated. (Rafael)
1170 Duping UTF-8 filehandles
1172 Duping a filehandle which has the ":utf8" PerlIO layer set will now
1173 properly carry that layer on the duped filehandle. (Rafael)
1174 Localisation of hash elements
1176 Localizing a hash element whose key was given as a variable didn't
1177 work correctly if the variable was changed while the local() was in
1178 effect (as in "local $h{$x}; ++$x"). (Bo Lindbergh)
1179
1181 Use of uninitialized value
1182 Perl will now try to tell you the name of the variable (if any)
1183 that was undefined.
1184 Deprecated use of my() in false conditional
1186 A new deprecation warning, Deprecated use of my() in false
1187 conditional, has been added, to warn against the use of the dubious
1188 and deprecated construct
1189 my $x if 0;
1191 See perldiag. Use "state" variables instead.
1193 !=~ should be !~
1195 A new warning, "!=~ should be !~", is emitted to prevent this
1196 misspelling of the non-matching operator.
1197 Newline in left-justified string
1199 The warning Newline in left-justified string has been removed.
1200 Too late for "-T" option
1202 The error Too late for "-T" option has been reformulated to be more
1203 descriptive.
1204 "%s" variable %s masks earlier declaration
1206 This warning is now emitted in more consistent cases; in short,
1207 when one of the declarations involved is a "my" variable:
1208 my $x; my $x; # warns
1210 my $x; our $x; # warns
1211 our $x; my $x; # warns
1212 On the other hand, the following:
1214 our $x; our $x;
1216 now gives a ""our" variable %s redeclared" warning.
1218 readdir()/closedir()/etc. attempted on invalid dirhandle
1220 These new warnings are now emitted when a dirhandle is used but is
1221 either closed or not really a dirhandle.
1222 Opening dirhandle/filehandle %s also as a file/directory
1224 Two deprecation warnings have been added: (Rafael)
1225 Opening dirhandle %s also as a file
1227 Opening filehandle %s also as a directory
1228 Use of -P is deprecated
1230 Perl's command-line switch "-P" is now deprecated.
1231 v-string in use/require is non-portable
1233 Perl will warn you against potential backwards compatibility
1234 problems with the "use VERSION" syntax.
1235 perl -V
1237 "perl -V" has several improvements, making it more useable from
1238 shell scripts to get the value of configuration variables. See
1239 perlrun for details.
1240
1242 In general, the source code of perl has been refactored, tidied up, and
1243 optimized in many places. Also, memory management and allocation has
1244 been improved in several points.
1245 When compiling the perl core with gcc, as many gcc warning flags are
1247 turned on as is possible on the platform. (This quest for cleanliness
1248 doesn't extend to XS code because we cannot guarantee the tidiness of
1249 code we didn't write.) Similar strictness flags have been added or
1250 tightened for various other C compilers.
1251 Reordering of SVt_* constants
1253 The relative ordering of constants that define the various types of
1254 "SV" have changed; in particular, "SVt_PVGV" has been moved before
1255 "SVt_PVLV", "SVt_PVAV", "SVt_PVHV" and "SVt_PVCV". This is unlikely to
1256 make any difference unless you have code that explicitly makes
1257 assumptions about that ordering. (The inheritance hierarchy of "B::*"
1258 objects has been changed to reflect this.)
1259 Elimination of SVt_PVBM
1261 Related to this, the internal type "SVt_PVBM" has been removed. This
1262 dedicated type of "SV" was used by the "index" operator and parts of
1263 the regexp engine to facilitate fast Boyer-Moore matches. Its use
1264 internally has been replaced by "SV"s of type "SVt_PVGV".
1265 New type SVt_BIND
1267 A new type "SVt_BIND" has been added, in readiness for the project to
1268 implement Perl 6 on 5. There deliberately is no implementation yet, and
1269 they cannot yet be created or destroyed.
1270 Removal of CPP symbols
1272 The C preprocessor symbols "PERL_PM_APIVERSION" and
1273 "PERL_XS_APIVERSION", which were supposed to give the version number of
1274 the oldest perl binary-compatible (resp. source-compatible) with the
1275 present one, were not used, and sometimes had misleading values. They
1276 have been removed.
1277 Less space is used by ops
1279 The "BASEOP" structure now uses less space. The "op_seq" field has been
1280 removed and replaced by a single bit bit-field "op_opt". "op_type" is
1281 now 9 bits long. (Consequently, the "B::OP" class doesn't provide an
1282 "seq" method anymore.)
1283 New parser
1285 perl's parser is now generated by bison (it used to be generated by
1286 byacc.) As a result, it seems to be a bit more robust.
1287 Also, Dave Mitchell improved the lexer debugging output under "-DT".
1289 Use of "const"
1291 Andy Lester supplied many improvements to determine which function
1292 parameters and local variables could actually be declared "const" to
1293 the C compiler. Steve Peters provided new *_set macros and reworked the
1294 core to use these rather than assigning to macros in LVALUE context.
1295 Mathoms
1297 A new file, mathoms.c, has been added. It contains functions that are
1298 no longer used in the perl core, but that remain available for binary
1299 or source compatibility reasons. However, those functions will not be
1300 compiled in if you add "-DNO_MATHOMS" in the compiler flags.
1301 "AvFLAGS" has been removed
1303 The "AvFLAGS" macro has been removed.
1304 "av_*" changes
1306 The "av_*()" functions, used to manipulate arrays, no longer accept
1307 null "AV*" parameters.
1308 $^H and %^H
1310 The implementation of the special variables $^H and %^H has changed, to
1311 allow implementing lexical pragmas in pure Perl.
1312 B:: modules inheritance changed
1314 The inheritance hierarchy of "B::" modules has changed; "B::NV" now
1315 inherits from "B::SV" (it used to inherit from "B::IV").
1316 Anonymous hash and array constructors
1318 The anonymous hash and array constructors now take 1 op in the optree
1319 instead of 3, now that pp_anonhash and pp_anonlist return a reference
1320 to an hash/array when the op is flagged with OPf_SPECIAL. (Nicholas
1321 Clark)
1322
1324 There's still a remaining problem in the implementation of the lexical
1325 $_: it doesn't work inside "/(?{...})/" blocks. (See the TODO test in
1326 t/op/mydef.t.)
1327 Stacked filetest operators won't work when the "filetest" pragma is in
1329 effect, because they rely on the stat() buffer "_" being populated, and
1330 filetest bypasses stat().
1331 UTF-8 problems
1333 The handling of Unicode still is unclean in several places, where it's
1334 dependent on whether a string is internally flagged as UTF-8. This will
1335 be made more consistent in perl 5.12, but that won't be possible
1336 without a certain amount of backwards incompatibility.
1337
1339 When compiled with g++ and thread support on Linux, it's reported that
1340 the $! stops working correctly. This is related to the fact that the
1341 glibc provides two strerror_r(3) implementation, and perl selects the
1342 wrong one.
1343
1345 If you find what you think is a bug, you might check the articles
1346 recently posted to the comp.lang.perl.misc newsgroup and the perl bug
1347 database at http://rt.perl.org/rt3/ . There may also be information at
1348 http://www.perl.org/ , the Perl Home Page.
1349 If you believe you have an unreported bug, please run the perlbug
1351 program included with your release. Be sure to trim your bug down to a
1352 tiny but sufficient test case. Your bug report, along with the output
1353 of "perl -V", will be sent off to perlbug@perl.org to be analysed by
1354 the Perl porting team.
1355
1357 The Changes file and the perl590delta to perl595delta man pages for
1358 exhaustive details on what changed.
1359 The INSTALL file for how to build Perl.
1361 The README file for general stuff.
1363 The Artistic and Copying files for copyright information.
1365perl v5.16.3 2013-03-04 PERL5100DELTA(1)