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1=encoding utf8
2
3=head1 NAME
4
5perl5200delta - what is new for perl v5.20.0
6
7=head1 DESCRIPTION
8
9This document describes differences between the 5.18.0 release and the
105.20.0 release.
11
12If you are upgrading from an earlier release such as 5.16.0, first read
13L<perl5180delta>, which describes differences between 5.16.0 and 5.18.0.
14
15=head1 Core Enhancements
16
17=head2 Experimental Subroutine signatures
18
19Declarative syntax to unwrap argument list into lexical variables.
20C<sub foo ($a,$b) {...}> checks the number of arguments and puts the
21arguments into lexical variables. Signatures are not equivalent to
22the existing idiom of C<sub foo { my($a,$b) = @_; ... }>. Signatures
23are only available by enabling a non-default feature, and generate
24warnings about being experimental. The syntactic clash with
25prototypes is managed by disabling the short prototype syntax when
26signatures are enabled.
27
28See L<perlsub/Signatures> for details.
29
30=head2 C<sub>s now take a C<prototype> attribute
31
32When declaring or defining a C<sub>, the prototype can now be specified inside
33of a C<prototype> attribute instead of in parens following the name.
34
35For example, C<sub foo($$){}> could be rewritten as
36C<sub foo : prototype($$){}>.
37
38=head2 More consistent prototype parsing
39
40Multiple semicolons in subroutine prototypes have long been tolerated and
41treated as a single semicolon. There was one case where this did not
42happen. A subroutine whose prototype begins with "*" or ";*" can affect
43whether a bareword is considered a method name or sub call. This now
44applies also to ";;;*".
45
46Whitespace has long been allowed inside subroutine prototypes, so
47C<sub( $ $ )> is equivalent to C<sub($$)>, but until now it was stripped
48when the subroutine was parsed. Hence, whitespace was I<not> allowed in
49prototypes set by C<Scalar::Util::set_prototype>. Now it is permitted,
50and the parser no longer strips whitespace. This means
51C<prototype &mysub> returns the original prototype, whitespace and all.
52
53=head2 C<rand> now uses a consistent random number generator
54
55Previously perl would use a platform specific random number generator, varying
56between the libc rand(), random() or drand48().
57
58This meant that the quality of perl's random numbers would vary from platform
59to platform, from the 15 bits of rand() on Windows to 48-bits on POSIX
60platforms such as Linux with drand48().
61
62Perl now uses its own internal drand48() implementation on all platforms. This
63does not make perl's C<rand> cryptographically secure. [perl #115928]
64
65=head2 New slice syntax
66
67The new C<%hash{...}> and C<%array[...]> syntax returns a list of key/value (or
68index/value) pairs. See L<perldata/"Key/Value Hash Slices">.
69
70=head2 Experimental Postfix Dereferencing
71
72When the C<postderef> feature is in effect, the following syntactical
73equivalencies are set up:
74
75 $sref->$*; # same as ${ $sref } # interpolates
76 $aref->@*; # same as @{ $aref } # interpolates
77 $href->%*; # same as %{ $href }
78 $cref->&*; # same as &{ $cref }
79 $gref->**; # same as *{ $gref }
80
81 $aref->$#*; # same as $#{ $aref }
82
83 $gref->*{ $slot }; # same as *{ $gref }{ $slot }
84
85 $aref->@[ ... ]; # same as @$aref[ ... ] # interpolates
86 $href->@{ ... }; # same as @$href{ ... } # interpolates
87 $aref->%[ ... ]; # same as %$aref[ ... ]
88 $href->%{ ... }; # same as %$href{ ... }
89
90Those marked as interpolating only interpolate if the associated
91C<postderef_qq> feature is also enabled. This feature is B<experimental> and
92will trigger C<experimental::postderef>-category warnings when used, unless
93they are suppressed.
94
95For more information, consult L<the Postfix Dereference Syntax section of
96perlref|perlref/Postfix Dereference Syntax>.
97
98=head2 Unicode 6.3 now supported
99
100Perl now supports and is shipped with Unicode 6.3 (though Perl may be
101recompiled with any previous Unicode release as well). A detailed list of
102Unicode 6.3 changes is at L<http://www.unicode.org/versions/Unicode6.3.0/>.
103
104=head2 New C<\p{Unicode}> regular expression pattern property
105
106This is a synonym for C<\p{Any}> and matches the set of Unicode-defined
107code points 0 - 0x10FFFF.
108
109=head2 Better 64-bit support
110
111On 64-bit platforms, the internal array functions now use 64-bit offsets,
112allowing Perl arrays to hold more than 2**31 elements, if you have the memory
113available.
114
115The regular expression engine now supports strings longer than 2**31
116characters. [perl #112790, #116907]
117
118The functions PerlIO_get_bufsiz, PerlIO_get_cnt, PerlIO_set_cnt and
119PerlIO_set_ptrcnt now have SSize_t, rather than int, return values and
120parameters.
121
122=head2 C<S<use locale>> now works on UTF-8 locales
123
124Until this release, only single-byte locales, such as the ISO 8859
125series were supported. Now, the increasingly common multi-byte UTF-8
126locales are also supported. A UTF-8 locale is one in which the
127character set is Unicode and the encoding is UTF-8. The POSIX
128C<LC_CTYPE> category operations (case changing (like C<lc()>, C<"\U">),
129and character classification (C<\w>, C<\D>, C<qr/[[:punct:]]/>)) under
130such a locale work just as if not under locale, but instead as if under
131C<S<use feature 'unicode_strings'>>, except taint rules are followed.
132Sorting remains by code point order in this release. [perl #56820].
133
134=head2 C<S<use locale>> now compiles on systems without locale ability
135
136Previously doing this caused the program to not compile. Within its
137scope the program behaves as if in the "C" locale. Thus programs
138written for platforms that support locales can run on locale-less
139platforms without change. Attempts to change the locale away from the
140"C" locale will, of course, fail.
141
142=head2 More locale initialization fallback options
143
144If there was an error with locales during Perl start-up, it immediately
145gave up and tried to use the C<"C"> locale. Now it first tries using
146other locales given by the environment variables, as detailed in
147L<perllocale/ENVIRONMENT>. For example, if C<LC_ALL> and C<LANG> are
148both set, and using the C<LC_ALL> locale fails, Perl will now try the
149C<LANG> locale, and only if that fails, will it fall back to C<"C">. On
150Windows machines, Perl will try, ahead of using C<"C">, the system
151default locale if all the locales given by environment variables fail.
152
153=head2 C<-DL> runtime option now added for tracing locale setting
154
155This is designed for Perl core developers to aid in field debugging bugs
156regarding locales.
157
158=head2 B<-F> now implies B<-a> and B<-a> implies B<-n>
159
160Previously B<-F> without B<-a> was a no-op, and B<-a> without B<-n> or B<-p>
161was a no-op, with this change, if you supply B<-F> then both B<-a> and B<-n>
162are implied and if you supply B<-a> then B<-n> is implied.
163
164You can still use B<-p> for its extra behaviour. [perl #116190]
165
166=head2 $a and $b warnings exemption
167
168The special variables $a and $b, used in C<sort>, are now exempt from "used
169once" warnings, even where C<sort> is not used. This makes it easier for
170CPAN modules to provide functions using $a and $b for similar purposes.
171[perl #120462]
172
173=head1 Security
174
175=head2 Avoid possible read of free()d memory during parsing
176
177It was possible that free()d memory could be read during parsing in the unusual
178circumstance of the Perl program ending with a heredoc and the last line of the
179file on disk having no terminating newline character. This has now been fixed.
180
181=head1 Incompatible Changes
182
183=head2 C<do> can no longer be used to call subroutines
184
185The C<do SUBROUTINE(LIST)> form has resulted in a deprecation warning
186since Perl v5.0.0, and is now a syntax error.
187
188=head2 Quote-like escape changes
189
190The character after C<\c> in a double-quoted string ("..." or qq(...))
191or regular expression must now be a printable character and may not be
192C<{>.
193
194A literal C<{> after C<\B> or C<\b> is now fatal.
195
196These were deprecated in perl v5.14.0.
197
198=head2 Tainting happens under more circumstances; now conforms to documentation
199
200This affects regular expression matching and changing the case of a
201string (C<lc>, C<"\U">, I<etc>.) within the scope of C<use locale>.
202The result is now tainted based on the operation, no matter what the
203contents of the string were, as the documentation (L<perlsec>,
204L<perllocale/SECURITY>) indicates it should. Previously, for the case
205change operation, if the string contained no characters whose case
206change could be affected by the locale, the result would not be tainted.
207For example, the result of C<uc()> on an empty string or one containing
208only above-Latin1 code points is now tainted, and wasn't before. This
209leads to more consistent tainting results. Regular expression patterns
210taint their non-binary results (like C<$&>, C<$2>) if and only if the
211pattern contains elements whose matching depends on the current
212(potentially tainted) locale. Like the case changing functions, the
213actual contents of the string being matched now do not matter, whereas
214formerly it did. For example, if the pattern contains a C<\w>, the
215results will be tainted even if the match did not have to use that
216portion of the pattern to succeed or fail, because what a C<\w> matches
217depends on locale. However, for example, a C<.> in a pattern will not
218enable tainting, because the dot matches any single character, and what
219the current locale is doesn't change in any way what matches and what
220doesn't.
221
222=head2 C<\p{}>, C<\P{}> matching has changed for non-Unicode code
223points.
224
225C<\p{}> and C<\P{}> are defined by Unicode only on Unicode-defined code
226points (C<U+0000> through C<U+10FFFF>). Their behavior on matching
227these legal Unicode code points is unchanged, but there are changes for
228code points C<0x110000> and above. Previously, Perl treated the result
229of matching C<\p{}> and C<\P{}> against these as C<undef>, which
230translates into "false". For C<\P{}>, this was then complemented into
231"true". A warning was supposed to be raised when this happened.
232However, various optimizations could prevent the warning, and the
233results were often counter-intuitive, with both a match and its seeming
234complement being false. Now all non-Unicode code points are treated as
235typical unassigned Unicode code points. This generally is more
236Do-What-I-Mean. A warning is raised only if the results are arguably
237different from a strict Unicode approach, and from what Perl used to do.
238Code that needs to be strictly Unicode compliant can make this warning
239fatal, and then Perl always raises the warning.
240
241Details are in L<perlunicode/Beyond Unicode code points>.
242
243=head2 C<\p{All}> has been expanded to match all possible code points
244
245The Perl-defined regular expression pattern element C<\p{All}>, unused
246on CPAN, used to match just the Unicode code points; now it matches all
247possible code points; that is, it is equivalent to C<qr/./s>. Thus
248C<\p{All}> is no longer synonymous with C<\p{Any}>, which continues to
249match just the Unicode code points, as Unicode says it should.
250
251=head2 Data::Dumper's output may change
252
253Depending on the data structures dumped and the settings set for
254Data::Dumper, the dumped output may have changed from previous
255versions.
256
257If you have tests that depend on the exact output of Data::Dumper,
258they may fail.
259
260To avoid this problem in your code, test against the data structure
261from evaluating the dumped structure, instead of the dump itself.
262
263=head2 Locale decimal point character no longer leaks outside of S<C<use locale>> scope
264
265This is actually a bug fix, but some code has come to rely on the bug
266being present, so this change is listed here. The current locale that
267the program is running under is not supposed to be visible to Perl code
268except within the scope of a S<C<use locale>>. However, until now under
269certain circumstances, the character used for a decimal point (often a
270comma) leaked outside the scope. If your code is affected by this
271change, simply add a S<C<use locale>>.
272
273=head2 Assignments of Windows sockets error codes to $! now prefer F<errno.h> values over WSAGetLastError() values
274
275In previous versions of Perl, Windows sockets error codes as returned by
276WSAGetLastError() were assigned to $!, and some constants such as ECONNABORTED,
277not in F<errno.h> in VC++ (or the various Windows ports of gcc) were defined to
278corresponding WSAE* values to allow $! to be tested against the E* constants
279exported by L<Errno> and L<POSIX>.
280
281This worked well until VC++ 2010 and later, which introduced new E* constants
282with values E<gt> 100 into F<errno.h>, including some being (re)defined by perl
283to WSAE* values. That caused problems when linking XS code against other
284libraries which used the original definitions of F<errno.h> constants.
285
286To avoid this incompatibility, perl now maps WSAE* error codes to E* values
287where possible, and assigns those values to $!. The E* constants exported by
288L<Errno> and L<POSIX> are updated to match so that testing $! against them,
289wherever previously possible, will continue to work as expected, and all E*
290constants found in F<errno.h> are now exported from those modules with their
291original F<errno.h> values.
292
293In order to avoid breakage in existing Perl code which assigns WSAE* values to
294$!, perl now intercepts the assignment and performs the same mapping to E*
295values as it uses internally when assigning to $! itself.
296
297However, one backwards-incompatibility remains: existing Perl code which
298compares $! against the numeric values of the WSAE* error codes that were
299previously assigned to $! will now be broken in those cases where a
300corresponding E* value has been assigned instead. This is only an issue for
301those E* values E<lt> 100, which were always exported from L<Errno> and
302L<POSIX> with their original F<errno.h> values, and therefore could not be used
303for WSAE* error code tests (e.g. WSAEINVAL is 10022, but the corresponding
304EINVAL is 22). (E* values E<gt> 100, if present, were redefined to WSAE*
305values anyway, so compatibility can be achieved by using the E* constants,
306which will work both before and after this change, albeit using different
307numeric values under the hood.)
308
309=head2 Functions C<PerlIO_vsprintf> and C<PerlIO_sprintf> have been removed
310
311These two functions, undocumented, unused in CPAN, and problematic, have been
312removed.
313
314=head1 Deprecations
315
316=head2 The C</\C/> character class
317
318The C</\C/> regular expression character class is deprecated. From perl
3195.22 onwards it will generate a warning, and from perl 5.24 onwards it
320will be a regular expression compiler error. If you need to examine the
321individual bytes that make up a UTF8-encoded character, then use
322C<utf8::encode()> on the string (or a copy) first.
323
324=head2 Literal control characters in variable names
325
326This deprecation affects things like $\cT, where \cT is a literal control (such
327as a C<NAK> or C<NEGATIVE ACKNOWLEDGE> character) in
328the source code. Surprisingly, it appears that originally this was intended as
329the canonical way of accessing variables like $^T, with the caret form only
330being added as an alternative.
331
332The literal control form is being deprecated for two main reasons. It has what
333are likely unfixable bugs, such as $\cI not working as an alias for $^I, and
334their usage not being portable to non-ASCII platforms: While $^T will work
335everywhere, \cT is whitespace in EBCDIC. [perl #119123]
336
337=head2 References to non-integers and non-positive integers in C<$/>
338
339Setting C<$/> to a reference to zero or a reference to a negative integer is
340now deprecated, and will behave B<exactly> as though it was set to C<undef>.
341If you want slurp behavior set C<$/> to C<undef> explicitly.
342
343Setting C<$/> to a reference to a non integer is now forbidden and will
344throw an error. Perl has never documented what would happen in this
345context and while it used to behave the same as setting C<$/> to
346the address of the references in future it may behave differently, so we
347have forbidden this usage.
348
349=head2 Character matching routines in POSIX
350
351Use of any of these functions in the C<POSIX> module is now deprecated:
352C<isalnum>, C<isalpha>, C<iscntrl>, C<isdigit>, C<isgraph>, C<islower>,
353C<isprint>, C<ispunct>, C<isspace>, C<isupper>, and C<isxdigit>. The
354functions are buggy and don't work on UTF-8 encoded strings. See their
355entries in L<POSIX> for more information.
356
357A warning is raised on the first call to any of them from each place in
358the code that they are called. (Hence a repeated statement in a loop
359will raise just the one warning.)
360
361=head2 Interpreter-based threads are now I<discouraged>
362
363The "interpreter-based threads" provided by Perl are not the fast, lightweight
364system for multitasking that one might expect or hope for. Threads are
365implemented in a way that make them easy to misuse. Few people know how to
366use them correctly or will be able to provide help.
367
368The use of interpreter-based threads in perl is officially
369L<discouraged|perlpolicy/discouraged>.
370
371=head2 Module removals
372
373The following modules will be removed from the core distribution in a
374future release, and will at that time need to be installed from CPAN.
375Distributions on CPAN which require these modules will need to list them as
376prerequisites.
377
378The core versions of these modules will now issue C<"deprecated">-category
379warnings to alert you to this fact. To silence these deprecation warnings,
380install the modules in question from CPAN.
381
382Note that the planned removal of these modules from core does not reflect a
383judgement about the quality of the code and should not be taken as a suggestion
384that their use be halted. Their disinclusion from core primarily hinges on
385their necessity to bootstrapping a fully functional, CPAN-capable Perl
386installation, not on concerns over their design.
387
388=over
389
390=item L<CGI> and its associated CGI:: packages
391
392=item L<inc::latest>
393
394=item L<Package::Constants>
395
396=item L<Module::Build> and its associated Module::Build:: packages
397
398=back
399
400=head2 Utility removals
401
402The following utilities will be removed from the core distribution in a
403future release, and will at that time need to be installed from CPAN.
404
405=over 4
406
407=item L<find2perl>
408
409=item L<s2p>
410
411=item L<a2p>
412
413=back
414
415=head1 Performance Enhancements
416
417=over 4
418
419=item *
420
421Perl has a new copy-on-write mechanism that avoids the need to copy the
422internal string buffer when assigning from one scalar to another. This
423makes copying large strings appear much faster. Modifying one of the two
424(or more) strings after an assignment will force a copy internally. This
425makes it unnecessary to pass strings by reference for efficiency.
426
427This feature was already available in 5.18.0, but wasn't enabled by
428default. It is the default now, and so you no longer need build perl with
429the F<Configure> argument:
430
431 -Accflags=-DPERL_NEW_COPY_ON_WRITE
432
433It can be disabled (for now) in a perl build with:
434
435 -Accflags=-DPERL_NO_COW
436
437On some operating systems Perl can be compiled in such a way that any
438attempt to modify string buffers shared by multiple SVs will crash. This
439way XS authors can test that their modules handle copy-on-write scalars
440correctly. See L<perlguts/"Copy on Write"> for detail.
441
442=item *
443
444Perl has an optimizer for regular expression patterns. It analyzes the pattern
445to find things such as the minimum length a string has to be to match, etc. It
446now better handles code points that are above the Latin1 range.
447
448=item *
449
450Executing a regex that contains the C<^> anchor (or its variant under the
451C</m> flag) has been made much faster in several situations.
452
453=item *
454
455Precomputed hash values are now used in more places during method lookup.
456
457=item *
458
459Constant hash key lookups (C<$hash{key}> as opposed to C<$hash{$key}>) have
460long had the internal hash value computed at compile time, to speed up
461lookup. This optimisation has only now been applied to hash slices as
462well.
463
464=item *
465
466Combined C<and> and C<or> operators in void context, like those
467generated for C<< unless ($a && $b) >> and C<< if ($a || b) >> now
468short circuit directly to the end of the statement. [perl #120128]
469
470=item *
471
472In certain situations, when C<return> is the last statement in a subroutine's
473main scope, it will be optimized out. This means code like:
474
475 sub baz { return $cat; }
476
477will now behave like:
478
479 sub baz { $cat; }
480
481which is notably faster.
482
483[perl #120765]
484
485=item *
486
487Code like:
488
489 my $x; # or @x, %x
490 my $y;
491
492is now optimized to:
493
494 my ($x, $y);
495
496In combination with the L<padrange optimization introduced in
497v5.18.0|perl5180delta/Internal Changes>, this means longer uninitialized my
498variable statements are also optimized, so:
499
500 my $x; my @y; my %z;
501
502becomes:
503
504 my ($x, @y, %z);
505
506[perl #121077]
507
508=item *
509
510The creation of certain sorts of lists, including array and hash slices, is now
511faster.
512
513=item *
514
515The optimisation for arrays indexed with a small constant integer is now
516applied for integers in the range -128..127, rather than 0..255. This should
517speed up Perl code using expressions like C<$x[-1]>, at the expense of
518(presumably much rarer) code using expressions like C<$x[200]>.
519
520=item *
521
522The first iteration over a large hash (using C<keys> or C<each>) is now
523faster. This is achieved by preallocating the hash's internal iterator
524state, rather than lazily creating it when the hash is first iterated. (For
525small hashes, the iterator is still created only when first needed. The
526assumption is that small hashes are more likely to be used as objects, and
527therefore never allocated. For large hashes, that's less likely to be true,
528and the cost of allocating the iterator is swamped by the cost of allocating
529space for the hash itself.)
530
531=item *
532
533When doing a global regex match on a string that came from the C<readline>
534or C<E<lt>E<gt>> operator, the data is no longer copied unnecessarily.
535[perl #121259]
536
537=item *
538
539Dereferencing (as in C<$obj-E<gt>[0]> or C<$obj-E<gt>{k}>) is now faster
540when C<$obj> is an instance of a class that has overloaded methods, but
541doesn't overload any of the dereferencing methods C<@{}>, C<%{}>, and so on.
542
543=item *
544
545Perl's optimiser no longer skips optimising code that follows certain
546C<eval {}> expressions (including those with an apparent infinite loop).
547
548=item *
549
550The implementation now does a better job of avoiding meaningless work at
551runtime. Internal effect-free "null" operations (created as a side-effect of
552parsing Perl programs) are normally deleted during compilation. That
553deletion is now applied in some situations that weren't previously handled.
554
555=item *
556
557Perl now does less disk I/O when dealing with Unicode properties that cover
558up to three ranges of consecutive code points.
559
560=back
561
562=head1 Modules and Pragmata
563
564=head2 New Modules and Pragmata
565
566=over 4
567
568=item *
569
570L<experimental> 0.007 has been added to the Perl core.
571
572=item *
573
574L<IO::Socket::IP> 0.29 has been added to the Perl core.
575
576=back
577
578=head2 Updated Modules and Pragmata
579
580=over 4
581
582=item *
583
584L<Archive::Tar> has been upgraded from version 1.90 to 1.96.
585
586=item *
587
588L<arybase> has been upgraded from version 0.06 to 0.07.
589
590=item *
591
592L<Attribute::Handlers> has been upgraded from version 0.94 to 0.96.
593
594=item *
595
596L<attributes> has been upgraded from version 0.21 to 0.22.
597
598=item *
599
600L<autodie> has been upgraded from version 2.13 to 2.23.
601
602=item *
603
604L<AutoLoader> has been upgraded from version 5.73 to 5.74.
605
606=item *
607
608L<autouse> has been upgraded from version 1.07 to 1.08.
609
610=item *
611
612L<B> has been upgraded from version 1.42 to 1.48.
613
614=item *
615
616L<B::Concise> has been upgraded from version 0.95 to 0.992.
617
618=item *
619
620L<B::Debug> has been upgraded from version 1.18 to 1.19.
621
622=item *
623
624L<B::Deparse> has been upgraded from version 1.20 to 1.26.
625
626=item *
627
628L<base> has been upgraded from version 2.18 to 2.22.
629
630=item *
631
632L<Benchmark> has been upgraded from version 1.15 to 1.18.
633
634=item *
635
636L<bignum> has been upgraded from version 0.33 to 0.37.
637
638=item *
639
640L<Carp> has been upgraded from version 1.29 to 1.3301.
641
642=item *
643
644L<CGI> has been upgraded from version 3.63 to 3.65.
645NOTE: L<CGI> is deprecated and may be removed from a future version of Perl.
646
647=item *
648
649L<charnames> has been upgraded from version 1.36 to 1.40.
650
651=item *
652
653L<Class::Struct> has been upgraded from version 0.64 to 0.65.
654
655=item *
656
657L<Compress::Raw::Bzip2> has been upgraded from version 2.060 to 2.064.
658
659=item *
660
661L<Compress::Raw::Zlib> has been upgraded from version 2.060 to 2.065.
662
663=item *
664
665L<Config::Perl::V> has been upgraded from version 0.17 to 0.20.
666
667=item *
668
669L<constant> has been upgraded from version 1.27 to 1.31.
670
671=item *
672
673L<CPAN> has been upgraded from version 2.00 to 2.05.
674
675=item *
676
677L<CPAN::Meta> has been upgraded from version 2.120921 to 2.140640.
678
679=item *
680
681L<CPAN::Meta::Requirements> has been upgraded from version 2.122 to 2.125.
682
683=item *
684
685L<CPAN::Meta::YAML> has been upgraded from version 0.008 to 0.012.
686
687=item *
688
689L<Data::Dumper> has been upgraded from version 2.145 to 2.151.
690
691=item *
692
693L<DB> has been upgraded from version 1.04 to 1.07.
694
695=item *
696
697L<DB_File> has been upgraded from version 1.827 to 1.831.
698
699=item *
700
701L<DBM_Filter> has been upgraded from version 0.05 to 0.06.
702
703=item *
704
705L<deprecate> has been upgraded from version 0.02 to 0.03.
706
707=item *
708
709L<Devel::Peek> has been upgraded from version 1.11 to 1.16.
710
711=item *
712
713L<Devel::PPPort> has been upgraded from version 3.20 to 3.21.
714
715=item *
716
717L<diagnostics> has been upgraded from version 1.31 to 1.34.
718
719=item *
720
721L<Digest::MD5> has been upgraded from version 2.52 to 2.53.
722
723=item *
724
725L<Digest::SHA> has been upgraded from version 5.84 to 5.88.
726
727=item *
728
729L<DynaLoader> has been upgraded from version 1.18 to 1.25.
730
731=item *
732
733L<Encode> has been upgraded from version 2.49 to 2.60.
734
735=item *
736
737L<encoding> has been upgraded from version 2.6_01 to 2.12.
738
739=item *
740
741L<English> has been upgraded from version 1.06 to 1.09.
742
743=item *
744
745L<Errno> has been upgraded from version 1.18 to 1.20_03.
746
747=item *
748
749L<Exporter> has been upgraded from version 5.68 to 5.70.
750
751=item *
752
753L<ExtUtils::CBuilder> has been upgraded from version 0.280210 to 0.280216.
754
755=item *
756
757L<ExtUtils::Command> has been upgraded from version 1.17 to 1.18.
758
759=item *
760
761L<ExtUtils::Embed> has been upgraded from version 1.30 to 1.32.
762
763=item *
764
765L<ExtUtils::Install> has been upgraded from version 1.59 to 1.67.
766
767=item *
768
769L<ExtUtils::MakeMaker> has been upgraded from version 6.66 to 6.98.
770
771=item *
772
773L<ExtUtils::Miniperl> has been upgraded from version to 1.01.
774
775=item *
776
777L<ExtUtils::ParseXS> has been upgraded from version 3.18 to 3.24.
778
779=item *
780
781L<ExtUtils::Typemaps> has been upgraded from version 3.19 to 3.24.
782
783=item *
784
785L<ExtUtils::XSSymSet> has been upgraded from version 1.2 to 1.3.
786
787=item *
788
789L<feature> has been upgraded from version 1.32 to 1.36.
790
791=item *
792
793L<fields> has been upgraded from version 2.16 to 2.17.
794
795=item *
796
797L<File::Basename> has been upgraded from version 2.84 to 2.85.
798
799=item *
800
801L<File::Copy> has been upgraded from version 2.26 to 2.29.
802
803=item *
804
805L<File::DosGlob> has been upgraded from version 1.10 to 1.12.
806
807=item *
808
809L<File::Fetch> has been upgraded from version 0.38 to 0.48.
810
811=item *
812
813L<File::Find> has been upgraded from version 1.23 to 1.27.
814
815=item *
816
817L<File::Glob> has been upgraded from version 1.20 to 1.23.
818
819=item *
820
821L<File::Spec> has been upgraded from version 3.40 to 3.47.
822
823=item *
824
825L<File::Temp> has been upgraded from version 0.23 to 0.2304.
826
827=item *
828
829L<FileCache> has been upgraded from version 1.08 to 1.09.
830
831=item *
832
833L<Filter::Simple> has been upgraded from version 0.89 to 0.91.
834
835=item *
836
837L<Filter::Util::Call> has been upgraded from version 1.45 to 1.49.
838
839=item *
840
841L<Getopt::Long> has been upgraded from version 2.39 to 2.42.
842
843=item *
844
845L<Getopt::Std> has been upgraded from version 1.07 to 1.10.
846
847=item *
848
849L<Hash::Util::FieldHash> has been upgraded from version 1.10 to 1.15.
850
851=item *
852
853L<HTTP::Tiny> has been upgraded from version 0.025 to 0.043.
854
855=item *
856
857L<I18N::Langinfo> has been upgraded from version 0.10 to 0.11.
858
859=item *
860
861L<I18N::LangTags> has been upgraded from version 0.39 to 0.40.
862
863=item *
864
865L<if> has been upgraded from version 0.0602 to 0.0603.
866
867=item *
868
869L<inc::latest> has been upgraded from version 0.4003 to 0.4205.
870NOTE: L<inc::latest> is deprecated and may be removed from a future version of Perl.
871
872=item *
873
874L<integer> has been upgraded from version 1.00 to 1.01.
875
876=item *
877
878L<IO> has been upgraded from version 1.28 to 1.31.
879
880=item *
881
882L<IO::Compress::Gzip> and friends have been upgraded from version 2.060 to
8832.064.
884
885=item *
886
887L<IPC::Cmd> has been upgraded from version 0.80 to 0.92.
888
889=item *
890
891L<IPC::Open3> has been upgraded from version 1.13 to 1.16.
892
893=item *
894
895L<IPC::SysV> has been upgraded from version 2.03 to 2.04.
896
897=item *
898
899L<JSON::PP> has been upgraded from version 2.27202 to 2.27203.
900
901=item *
902
903L<List::Util> has been upgraded from version 1.27 to 1.38.
904
905=item *
906
907L<locale> has been upgraded from version 1.02 to 1.03.
908
909=item *
910
911L<Locale::Codes> has been upgraded from version 3.25 to 3.30.
912
913=item *
914
915L<Locale::Maketext> has been upgraded from version 1.23 to 1.25.
916
917=item *
918
919L<Math::BigInt> has been upgraded from version 1.9991 to 1.9993.
920
921=item *
922
923L<Math::BigInt::FastCalc> has been upgraded from version 0.30 to 0.31.
924
925=item *
926
927L<Math::BigRat> has been upgraded from version 0.2604 to 0.2606.
928
929=item *
930
931L<MIME::Base64> has been upgraded from version 3.13 to 3.14.
932
933=item *
934
935L<Module::Build> has been upgraded from version 0.4003 to 0.4205.
936NOTE: L<Module::Build> is deprecated and may be removed from a future version of Perl.
937
938=item *
939
940L<Module::CoreList> has been upgraded from version 2.89 to 3.10.
941
942=item *
943
944L<Module::Load> has been upgraded from version 0.24 to 0.32.
945
946=item *
947
948L<Module::Load::Conditional> has been upgraded from version 0.54 to 0.62.
949
950=item *
951
952L<Module::Metadata> has been upgraded from version 1.000011 to 1.000019.
953
954=item *
955
956L<mro> has been upgraded from version 1.11 to 1.16.
957
958=item *
959
960L<Net::Ping> has been upgraded from version 2.41 to 2.43.
961
962=item *
963
964L<Opcode> has been upgraded from version 1.25 to 1.27.
965
966=item *
967
968L<Package::Constants> has been upgraded from version 0.02 to 0.04.
969NOTE: L<Package::Constants> is deprecated and may be removed from a future version of Perl.
970
971=item *
972
973L<Params::Check> has been upgraded from version 0.36 to 0.38.
974
975=item *
976
977L<parent> has been upgraded from version 0.225 to 0.228.
978
979=item *
980
981L<Parse::CPAN::Meta> has been upgraded from version 1.4404 to 1.4414.
982
983=item *
984
985L<Perl::OSType> has been upgraded from version 1.003 to 1.007.
986
987=item *
988
989L<perlfaq> has been upgraded from version 5.0150042 to 5.0150044.
990
991=item *
992
993L<PerlIO> has been upgraded from version 1.07 to 1.09.
994
995=item *
996
997L<PerlIO::encoding> has been upgraded from version 0.16 to 0.18.
998
999=item *
1000
1001L<PerlIO::scalar> has been upgraded from version 0.16 to 0.18.
1002
1003=item *
1004
1005L<PerlIO::via> has been upgraded from version 0.12 to 0.14.
1006
1007=item *
1008
1009L<Pod::Escapes> has been upgraded from version 1.04 to 1.06.
1010
1011=item *
1012
1013L<Pod::Functions> has been upgraded from version 1.06 to 1.08.
1014
1015=item *
1016
1017L<Pod::Html> has been upgraded from version 1.18 to 1.21.
1018
1019=item *
1020
1021L<Pod::Parser> has been upgraded from version 1.60 to 1.62.
1022
1023=item *
1024
1025L<Pod::Perldoc> has been upgraded from version 3.19 to 3.23.
1026
1027=item *
1028
1029L<Pod::Usage> has been upgraded from version 1.61 to 1.63.
1030
1031=item *
1032
1033L<POSIX> has been upgraded from version 1.32 to 1.38_03.
1034
1035=item *
1036
1037L<re> has been upgraded from version 0.23 to 0.26.
1038
1039=item *
1040
1041L<Safe> has been upgraded from version 2.35 to 2.37.
1042
1043=item *
1044
1045L<Scalar::Util> has been upgraded from version 1.27 to 1.38.
1046
1047=item *
1048
1049L<SDBM_File> has been upgraded from version 1.09 to 1.11.
1050
1051=item *
1052
1053L<Socket> has been upgraded from version 2.009 to 2.013.
1054
1055=item *
1056
1057L<Storable> has been upgraded from version 2.41 to 2.49.
1058
1059=item *
1060
1061L<strict> has been upgraded from version 1.07 to 1.08.
1062
1063=item *
1064
1065L<subs> has been upgraded from version 1.01 to 1.02.
1066
1067=item *
1068
1069L<Sys::Hostname> has been upgraded from version 1.17 to 1.18.
1070
1071=item *
1072
1073L<Sys::Syslog> has been upgraded from version 0.32 to 0.33.
1074
1075=item *
1076
1077L<Term::Cap> has been upgraded from version 1.13 to 1.15.
1078
1079=item *
1080
1081L<Term::ReadLine> has been upgraded from version 1.12 to 1.14.
1082
1083=item *
1084
1085L<Test::Harness> has been upgraded from version 3.26 to 3.30.
1086
1087=item *
1088
1089L<Test::Simple> has been upgraded from version 0.98 to 1.001002.
1090
1091=item *
1092
1093L<Text::ParseWords> has been upgraded from version 3.28 to 3.29.
1094
1095=item *
1096
1097L<Text::Tabs> has been upgraded from version 2012.0818 to 2013.0523.
1098
1099=item *
1100
1101L<Text::Wrap> has been upgraded from version 2012.0818 to 2013.0523.
1102
1103=item *
1104
1105L<Thread> has been upgraded from version 3.02 to 3.04.
1106
1107=item *
1108
1109L<Thread::Queue> has been upgraded from version 3.02 to 3.05.
1110
1111=item *
1112
1113L<threads> has been upgraded from version 1.86 to 1.93.
1114
1115=item *
1116
1117L<threads::shared> has been upgraded from version 1.43 to 1.46.
1118
1119=item *
1120
1121L<Tie::Array> has been upgraded from version 1.05 to 1.06.
1122
1123=item *
1124
1125L<Tie::File> has been upgraded from version 0.99 to 1.00.
1126
1127=item *
1128
1129L<Tie::Hash> has been upgraded from version 1.04 to 1.05.
1130
1131=item *
1132
1133L<Tie::Scalar> has been upgraded from version 1.02 to 1.03.
1134
1135=item *
1136
1137L<Tie::StdHandle> has been upgraded from version 4.3 to 4.4.
1138
1139=item *
1140
1141L<Time::HiRes> has been upgraded from version 1.9725 to 1.9726.
1142
1143=item *
1144
1145L<Time::Piece> has been upgraded from version 1.20_01 to 1.27.
1146
1147=item *
1148
1149L<Unicode::Collate> has been upgraded from version 0.97 to 1.04.
1150
1151=item *
1152
1153L<Unicode::Normalize> has been upgraded from version 1.16 to 1.17.
1154
1155=item *
1156
1157L<Unicode::UCD> has been upgraded from version 0.51 to 0.57.
1158
1159=item *
1160
1161L<utf8> has been upgraded from version 1.10 to 1.13.
1162
1163=item *
1164
1165L<version> has been upgraded from version 0.9902 to 0.9908.
1166
1167=item *
1168
1169L<vmsish> has been upgraded from version 1.03 to 1.04.
1170
1171=item *
1172
1173L<warnings> has been upgraded from version 1.18 to 1.23.
1174
1175=item *
1176
1177L<Win32> has been upgraded from version 0.47 to 0.49.
1178
1179=item *
1180
1181L<XS::Typemap> has been upgraded from version 0.10 to 0.13.
1182
1183=item *
1184
1185L<XSLoader> has been upgraded from version 0.16 to 0.17.
1186
1187=back
1188
1189=head1 Documentation
1190
1191=head2 New Documentation
1192
1193=head3 L<perlrepository>
1194
1195This document was removed (actually, renamed L<perlgit> and given a major
1196overhaul) in Perl v5.14, causing Perl documentation websites to show the now
1197out of date version in Perl v5.12 as the latest version. It has now been
1198restored in stub form, directing readers to current information.
1199
1200=head2 Changes to Existing Documentation
1201
1202=head3 L<perldata>
1203
1204=over 4
1205
1206=item *
1207
1208New sections have been added to document the new index/value array slice and
1209key/value hash slice syntax.
1210
1211=back
1212
1213=head3 L<perldebguts>
1214
1215=over 4
1216
1217=item *
1218
1219The C<DB::goto> and C<DB::lsub> debugger subroutines are now documented. [perl
1220#77680]
1221
1222=back
1223
1224=head3 L<perlexperiment>
1225
1226=over
1227
1228=item *
1229
1230C<\s> matching C<\cK> is marked experimental.
1231
1232=item *
1233
1234ithreads were accepted in v5.8.0 (but are discouraged as of v5.20.0).
1235
1236=item *
1237
1238Long doubles are not considered experimental.
1239
1240=item *
1241
1242Code in regular expressions, regular expression backtracking verbs,
1243and lvalue subroutines are no longer listed as experimental. (This
1244also affects L<perlre> and L<perlsub>.)
1245
1246=back
1247
1248=head3 L<perlfunc>
1249
1250=over
1251
1252=item *
1253
1254C<chop> and C<chomp> now note that they can reset the hash iterator.
1255
1256=item *
1257
1258C<exec>'s handling of arguments is now more clearly documented.
1259
1260=item *
1261
1262C<eval EXPR> now has caveats about expanding floating point numbers in some
1263locales.
1264
1265=item *
1266
1267C<goto EXPR> is now documented to handle an expression that evalutes to a
1268code reference as if it was C<goto &$coderef>. This behavior is at least ten
1269years old.
1270
1271=item *
1272
1273Since Perl v5.10, it has been possible for subroutines in C<@INC> to return
1274a reference to a scalar holding initial source code to prepend to the file.
1275This is now documented.
1276
1277=item *
1278
1279The documentation of C<ref> has been updated to recommend the use of
1280C<blessed>, C<isa> and C<reftype> when dealing with references to blessed
1281objects.
1282
1283=back
1284
1285=head3 L<perlguts>
1286
1287=over 4
1288
1289=item *
1290
1291Numerous minor changes have been made to reflect changes made to the perl
1292internals in this release.
1293
1294=item *
1295
1296New sections on L<Read-Only Values|perlguts/"Read-Only Values"> and
1297L<Copy on Write|perlguts/"Copy on Write"> have been added.
1298
1299=back
1300
1301=head3 L<perlhack>
1302
1303=over 4
1304
1305=item *
1306
1307The L<Super Quick Patch Guide|perlhack/SUPER QUICK PATCH GUIDE> section has
1308been updated.
1309
1310=back
1311
1312=head3 L<perlhacktips>
1313
1314=over 4
1315
1316=item *
1317
1318The documentation has been updated to include some more examples of C<gdb>
1319usage.
1320
1321=back
1322
736c79db 1323=head3 L<perllexwarn>
238894db
RS
1324
1325=over 4
1326
1327=item *
1328
1329The L<perllexwarn> documentation used to describe the hierarchy of warning
1330categories understood by the L<warnings> pragma. That description has now
1331been moved to the L<warnings> documentation itself, leaving L<perllexwarn>
1332as a stub that points to it. This change consolidates all documentation for
1333lexical warnings in a single place.
1334
1335=back
1336
1337=head3 L<perllocale>
1338
1339=over
1340
1341=item *
1342
1343The documentation now mentions F<fc()> and C<\F>, and includes many
1344clarifications and corrections in general.
1345
1346=back
1347
1348=head3 L<perlop>
1349
1350=over 4
1351
1352=item *
1353
1354The language design of Perl has always called for monomorphic operators.
1355This is now mentioned explicitly.
1356
1357=back
1358
1359=head3 L<perlopentut>
1360
1361=over 4
1362
1363=item *
1364
1365The C<open> tutorial has been completely rewritten by Tom Christiansen, and now
1366focuses on covering only the basics, rather than providing a comprehensive
1367reference to all things openable. This rewrite came as the result of a
1368vigorous discussion on perl5-porters kicked off by a set of improvements
1369written by Alexander Hartmaier to the existing L<perlopentut>. A "more than
1370you ever wanted to know about C<open>" document may follow in subsequent
1371versions of perl.
1372
1373=back
1374
1375=head3 L<perlre>
1376
1377=over 4
1378
1379=item *
1380
1381The fact that the regexp engine makes no effort to call (?{}) and (??{})
1382constructs any specified number of times (although it will basically DWIM
1383in case of a successful match) has been documented.
1384
1385=item *
1386
1387The C</r> modifier (for non-destructive substitution) is now documented. [perl
1388#119151]
1389
1390=item *
1391
1392The documentation for C</x> and C<(?# comment)> has been expanded and clarified.
1393
1394=back
1395
1396=head3 L<perlreguts>
1397
1398=over 4
1399
1400=item *
1401
1402The documentation has been updated in the light of recent changes to
1403F<regcomp.c>.
1404
1405=back
1406
1407=head3 L<perlsub>
1408
1409=over 4
1410
1411=item *
1412
1413The need to predeclare recursive functions with prototypes in order for the
1414prototype to be honoured in the recursive call is now documented. [perl #2726]
1415
1416=item *
1417
1418A list of subroutine names used by the perl implementation is now included.
1419[perl #77680]
1420
1421=back
1422
1423=head3 L<perltrap>
1424
1425=over 4
1426
1427=item *
1428
1429There is now a L<JavaScript|perltrap/JavaScript Traps> section.
1430
1431=back
1432
1433=head3 L<perlunicode>
1434
1435=over 4
1436
1437=item *
1438
1439The documentation has been updated to reflect C<Bidi_Class> changes in
1440Unicode 6.3.
1441
1442=back
1443
1444=head3 L<perlvar>
1445
1446=over 4
1447
1448=item *
1449
1450A new section explaining the performance issues of $`, $& and $', including
1451workarounds and changes in different versions of Perl, has been added.
1452
1453=item *
1454
1455Three L<English> variable names which have long been documented but do not
1456actually exist have been removed from the documentation. These were
1457C<$OLD_PERL_VERSION>, C<$OFMT>, and C<$ARRAY_BASE>.
1458
1459=back
1460
1461=head3 L<perlxs>
1462
1463=over 4
1464
1465=item *
1466
1467Several problems in the C<MY_CXT> example have been fixed.
1468
1469=back
1470
1471=head1 Diagnostics
1472
1473The following additions or changes have been made to diagnostic output,
1474including warnings and fatal error messages. For the complete list of
1475diagnostic messages, see L<perldiag>.
1476
1477=head2 New Diagnostics
1478
1479=head3 New Errors
1480
1481=over 4
1482
1483=item *
1484
1485L<delete argument is indexE<sol>value array slice, use array slice|perldiag/"delete argument is index/value array slice, use array slice">
1486
1487(F) You used index/value array slice syntax (C<%array[...]>) as the argument to
1488C<delete>. You probably meant C<@array[...]> with an @ symbol instead.
1489
1490=item *
1491
1492L<delete argument is keyE<sol>value hash slice, use hash slice|perldiag/"delete argument is key/value hash slice, use hash slice">
1493
1494(F) You used key/value hash slice syntax (C<%hash{...}>) as the argument to
1495C<delete>. You probably meant C<@hash{...}> with an @ symbol instead.
1496
1497=item *
1498
1499L<Magical list constants are not supported|perldiag/"Magical list constants are
1500not supported">
1501
1502(F) You assigned a magical array to a stash element, and then tried to use the
1503subroutine from the same slot. You are asking Perl to do something it cannot
1504do, details subject to change between Perl versions.
1505
1506=item *
1507
1508Added L<Setting $E<sol> to a %s reference is forbidden|perldiag/"Setting $E<sol> to %s reference is forbidden">
1509
1510=back
1511
1512=head3 New Warnings
1513
1514=over 4
1515
1516=item *
1517
1518L<%s on reference is experimental|perldiag/"push on reference is experimental">:
1519
1520The "auto-deref" feature is experimental.
1521
1522Starting in v5.14.0, it was possible to use push, pop, keys, and other
1523built-in functions not only on aggregate types, but on references to
1524them. The feature was not deployed to its original intended
1525specification, and now may become redundant to postfix dereferencing.
1526It has always been categorized as an experimental feature, and in
1527v5.20.0 is carries a warning as such.
1528
1529Warnings will now be issued at compile time when these operations are
1530detected.
1531
1532 no if $] >= 5.01908, warnings => "experimental::autoderef";
1533
1534Consider, though, replacing the use of these features, as they may
1535change behavior again before becoming stable.
1536
1537=item *
1538
1539L<A sequence of multiple spaces in a charnames alias definition is deprecated|perldiag/"A sequence of multiple spaces in a charnames alias definition is deprecated">
1540
1541L<Trailing white-space in a charnames alias definition is deprecated|perldiag/"Trailing white-space in a charnames alias definition is deprecated">
1542
1543These two deprecation warnings involving C<\N{...}> were incorrectly
1544implemented. They did not warn by default (now they do) and could not be
1545made fatal via C<< use warnings FATAL => 'deprecated' >> (now they can).
1546
1547=item *
1548
1549L<Attribute prototype(%s) discards earlier prototype attribute in same sub|perldiag/"Attribute prototype(%s) discards earlier prototype attribute in same sub">
1550
1551(W misc) A sub was declared as C<sub foo : prototype(A) : prototype(B) {}>, for
1552example. Since each sub can only have one prototype, the earlier
1553declaration(s) are discarded while the last one is applied.
1554
1555=item *
1556
1557L<Invalid \0 character in %s for %s: %s\0%s|perldiag/"Invalid \0 character in %s for %s: %s\0%s">
1558
1559(W syscalls) Embedded \0 characters in pathnames or other system call arguments
1560produce a warning as of 5.20. The parts after the \0 were formerly ignored by
1561system calls.
1562
1563=item *
1564
1565L<Matched non-Unicode code point 0x%X against Unicode property; may not be portable|perldiag/"Matched non-Unicode code point 0x%X against Unicode property; may not be portable">.
1566
1567This replaces the message "Code point 0x%X is not Unicode, all \p{} matches
1568fail; all \P{} matches succeed".
1569
1570=item *
1571
1572L<Missing ']' in prototype for %s : %s|perldiag/"Missing ']' in prototype for %s : %s">
1573
1574(W illegalproto) A grouping was started with C<[> but never closed with C<]>.
1575
1576=item *
1577
1578L<Possible precedence issue with control flow operator|perldiag/"Possible precedence issue with control flow operator">
1579
1580(W syntax) There is a possible problem with the mixing of a control flow
1581operator (e.g. C<return>) and a low-precedence operator like C<or>. Consider:
1582
1583 sub { return $a or $b; }
1584
1585This is parsed as:
1586
1587 sub { (return $a) or $b; }
1588
1589Which is effectively just:
1590
1591 sub { return $a; }
1592
1593Either use parentheses or the high-precedence variant of the operator.
1594
1595Note this may be also triggered for constructs like:
1596
1597 sub { 1 if die; }
1598
1599=item *
1600
1601L<Postfix dereference is experimental|perldiag/"Postfix dereference is experimental">
1602
1603(S experimental::postderef) This warning is emitted if you use the experimental
1604postfix dereference syntax. Simply suppress the warning if you want to use the
1605feature, but know that in doing so you are taking the risk of using an
1606experimental feature which may change or be removed in a future Perl version:
1607
1608 no warnings "experimental::postderef";
1609 use feature "postderef", "postderef_qq";
1610 $ref->$*;
1611 $aref->@*;
1612 $aref->@[@indices];
1613 ... etc ...
1614
1615=item *
1616
1617L<Prototype '%s' overridden by attribute 'prototype(%s)' in %s|perldiag/"Prototype '%s' overridden by attribute 'prototype(%s)' in %s">
1618
1619(W prototype) A prototype was declared in both the parentheses after the sub
1620name and via the prototype attribute. The prototype in parentheses is useless,
1621since it will be replaced by the prototype from the attribute before it's ever
1622used.
1623
1624=item *
1625
1626L<Scalar value @%s[%s] better written as $%s[%s]|perldiag/"Scalar value @%s[%s] better written as $%s[%s]">
1627
1628(W syntax) In scalar context, you've used an array index/value slice (indicated
1629by %) to select a single element of an array. Generally it's better to ask for
1630a scalar value (indicated by $). The difference is that C<$foo[&bar]> always
1631behaves like a scalar, both in the value it returns and when evaluating its
1632argument, while C<%foo[&bar]> provides a list context to its subscript, which
1633can do weird things if you're expecting only one subscript. When called in
1634list context, it also returns the index (what C<&bar> returns) in addition to
1635the value.
1636
1637=item *
1638
1639L<Scalar value @%s{%s} better written as $%s{%s}|perldiag/"Scalar value @%s{%s} better written as $%s{%s}">
1640
1641(W syntax) In scalar context, you've used a hash key/value slice (indicated by
1642%) to select a single element of a hash. Generally it's better to ask for a
1643scalar value (indicated by $). The difference is that C<$foo{&bar}> always
1644behaves like a scalar, both in the value it returns and when evaluating its
1645argument, while C<@foo{&bar}> and provides a list context to its subscript,
1646which can do weird things if you're expecting only one subscript. When called
1647in list context, it also returns the key in addition to the value.
1648
1649=item *
1650
1651L<Setting $E<sol> to a reference to %s as a form of slurp is deprecated, treating as undef|perldiag/"Setting $E<sol> to a reference to %s as a form of slurp is deprecated, treating as undef">
1652
1653=item *
1654
1655L<Unexpected exit %u|perldiag/"Unexpected exit %u">
1656
1657(S) exit() was called or the script otherwise finished gracefully when
1658C<PERL_EXIT_WARN> was set in C<PL_exit_flags>.
1659
1660=item *
1661
1662L<Unexpected exit failure %d|perldiag/"Unexpected exit failure %d">
1663
1664(S) An uncaught die() was called when C<PERL_EXIT_WARN> was set in
1665C<PL_exit_flags>.
1666
1667=item *
1668
1669L<Use of literal control characters in variable names is deprecated|perldiag/"Use of literal control characters in variable names is deprecated">
1670
1671(D deprecated) Using literal control characters in the source to refer to the
1672^FOO variables, like $^X and ${^GLOBAL_PHASE} is now deprecated. This only
1673affects code like $\cT, where \cT is a control (like a C<SOH>) in the
1674source code: ${"\cT"} and $^T remain valid.
1675
1676=item *
1677
1678L<Useless use of greediness modifier|perldiag/"Useless use of greediness modifier '%c' in regex; marked by <-- HERE in m/%s/">
1679
1680This fixes [Perl #42957].
1681
1682=back
1683
1684=head2 Changes to Existing Diagnostics
1685
1686=over 4
1687
1688=item *
1689
1690Warnings and errors from the regexp engine are now UTF-8 clean.
1691
1692=item *
1693
1694The "Unknown switch condition" error message has some slight changes. This
1695error triggers when there is an unknown condition in a C<(?(foo))> conditional.
1696The error message used to read:
1697
1698 Unknown switch condition (?(%s in regex;
1699
1700But what %s could be was mostly up to luck. For C<(?(foobar))>, you might have
1701seen "fo" or "f". For Unicode characters, you would generally get a corrupted
1702string. The message has been changed to read:
1703
1704 Unknown switch condition (?(...)) in regex;
1705
1706Additionally, the C<'E<lt>-- HERE'> marker in the error will now point to the
1707correct spot in the regex.
1708
1709=item *
1710
1711The "%s "\x%X" does not map to Unicode" warning is now correctly listed as a
1712severe warning rather than as a fatal error.
1713
1714=item *
1715
1716Under rare circumstances, one could get a "Can't coerce readonly REF to
1717string" instead of the customary "Modification of a read-only value". This
1718alternate error message has been removed.
1719
1720=item *
1721
1722"Ambiguous use of * resolved as operator *": This and similar warnings
1723about "%" and "&" used to occur in some circumstances where there was no
1724operator of the type cited, so the warning was completely wrong. This has
1725been fixed [perl #117535, #76910].
1726
1727=item *
1728
1729Warnings about malformed subroutine prototypes are now more consistent in
1730how the prototypes are rendered. Some of these warnings would truncate
1731prototypes containing nulls. In other cases one warning would suppress
1732another. The warning about illegal characters in prototypes no longer says
1733"after '_'" if the bad character came before the underscore.
1734
1735=item *
1736
1737L<Perl folding rules are not up-to-date for 0x%X; please use the perlbug
1738utility to report; in regex; marked by <-- HERE in
1739mE<sol>%sE<sol>|perldiag/"Perl folding rules are not up-to-date for 0x%X;
1740please use the perlbug utility to report; in regex; marked by <-- HERE in
1741m/%s/">
1742
1743This message is now only in the regexp category, and not in the deprecated
1744category. It is still a default (i.e., severe) warning [perl #89648].
1745
1746=item *
1747
1748L<%%s[%s] in scalar context better written as $%s[%s]|perldiag/"%%s[%s] in scalar context better written as $%s[%s]">
1749
1750This warning now occurs for any C<%array[$index]> or C<%hash{key}> known to
1751be in scalar context at compile time. Previously it was worded "Scalar
1752value %%s[%s] better written as $%s[%s]".
1753
1754=item *
1755
1756L<Switch condition not recognized in regex; marked by <-- HERE in mE<sol>%sE<sol>|perldiag/"Switch condition not recognized in regex; marked by <-- HERE in m/%s/">:
1757
1758The description for this diagnostic has been extended to cover all cases where the warning may occur.
1759Issues with the positioning of the arrow indicator have also been resolved.
1760
1761=item *
1762
1763The error messages for C<my($a?$b$c)> and C<my(do{})> now mention "conditional
1764expression" and "do block", respectively, instead of reading 'Can't declare
1765null operation in "my"'.
1766
1767=item *
1768
1769When C<use re "debug"> executes a regex containing a backreference, the
1770debugging output now shows what string is being matched.
1771
1772=item *
1773
1774The now fatal error message C<Character following "\c" must be ASCII> has been
1775reworded as C<Character following "\c" must be printable ASCII> to emphasize
1776that in C<\cI<X>>, I<X> must be a I<printable (non-control)> ASCII character.
1777
1778=back
1779
1780=head1 Utility Changes
1781
1782=head3 L<a2p>
1783
1784=over 4
1785
1786=item *
1787
1788A possible crash from an off-by-one error when trying to access before the
1789beginning of a buffer has been fixed. [perl #120244]
1790
1791=back
1792
1793=head3 F<bisect.pl>
1794
1795The git bisection tool F<Porting/bisect.pl> has had many enhancements.
1796
1797It is provided as part of the source distribution but not installed because
1798it is not self-contained as it relies on being run from within a git
1799checkout. Note also that it makes no attempt to fix tests, correct runtime
1800bugs or make something useful to install - its purpose is to make minimal
1801changes to get any historical revision of interest to build and run as close
1802as possible to "as-was", and thereby make C<git bisect> easy to use.
1803
1804=over 4
1805
1806=item *
1807
1808Can optionally run the test case with a timeout.
1809
1810=item *
1811
1812Can now run in-place in a clean git checkout.
1813
1814=item *
1815
1816Can run the test case under C<valgrind>.
1817
1818=item *
1819
1820Can apply user supplied patches and fixes to the source checkout before
1821building.
1822
1823=item *
1824
1825Now has fixups to enable building several more historical ranges of bleadperl,
1826which can be useful for pinpointing the origins of bugs or behaviour changes.
1827
1828=back
1829
1830=head3 L<find2perl>
1831
1832=over 4
1833
1834=item *
1835
1836L<find2perl> now handles C<?> wildcards correctly. [perl #113054]
1837
1838=back
1839
1840=head3 L<perlbug>
1841
1842=over 4
1843
1844=item *
1845
1846F<perlbug> now has a C<-p> option for attaching patches with a bug report.
1847
1848=item *
1849
1850L<perlbug> has been modified to supply the report template with CRLF line
1851endings on Windows.
1852[L<perl #121277|https://rt.perl.org/Public/Bug/Display.html?id=121277>]
1853
1854=item *
1855
1856L<perlbug> now makes as few assumptions as possible about the encoding of the
1857report. This will likely change in the future to assume UTF-8 by default but
1858allow a user override.
1859
1860=back
1861
1862=head1 Configuration and Compilation
1863
1864=over 4
1865
1866=item *
1867
1868The F<Makefile.PL> for L<SDBM_File> now generates a better F<Makefile>, which
1869avoids a race condition during parallel makes, which could cause the build to
1870fail. This is the last known parallel make problem (on *nix platforms), and
1871therefore we believe that a parallel make should now always be error free.
1872
1873=item *
1874
1875F<installperl> and F<installman>'s option handling has been refactored to use
1876L<Getopt::Long>. Both are used by the F<Makefile> C<install> targets, and
1877are not installed, so these changes are only likely to affect custom
1878installation scripts.
1879
1880=over 4
1881
1882=item *
1883
1884Single letter options now also have long names.
1885
1886=item *
1887
1888Invalid options are now rejected.
1889
1890=item *
1891
1892Command line arguments that are not options are now rejected.
1893
1894=item *
1895
1896Each now has a C<--help> option to display the usage message.
1897
1898=back
1899
1900The behaviour for all valid documented invocations is unchanged.
1901
1902=item *
1903
1904Where possible, the build now avoids recursive invocations of F<make> when
1905building pure-Perl extensions, without removing any parallelism from the
1906build. Currently around 80 extensions can be processed directly by the
1907F<make_ext.pl> tool, meaning that 80 invocations of F<make> and 160
1908invocations of F<miniperl> are no longer made.
1909
1910=item *
1911
1912The build system now works correctly when compiling under GCC or Clang with
1913link-time optimization enabled (the C<-flto> option). [perl #113022]
1914
1915=item *
1916
1917Distinct library basenames with C<d_libname_unique>.
1918
1919When compiling perl with this option, the library files for XS modules are
1920named something "unique" -- for example, Hash/Util/Util.so becomes
1921Hash/Util/PL_Hash__Util.so. This behavior is similar to what currently
1922happens on VMS, and serves as groundwork for the Android port.
1923
1924=item *
1925
1926C<sysroot> option to indicate the logical root directory under gcc and clang.
1927
1928When building with this option set, both Configure and the compilers search
1929for all headers and libraries under this new sysroot, instead of /.
1930
1931This is a huge time saver if cross-compiling, but can also help
1932on native builds if your toolchain's files have non-standard locations.
1933
1934=item *
1935
1936The cross-compilation model has been renovated.
1937There's several new options, and some backwards-incompatible changes:
1938
1939We now build binaries for miniperl and generate_uudmap to be used on the host,
1940rather than running every miniperl call on the target; this means that, short
1941of 'make test', we no longer need access to the target system once Configure is
1942done. You can provide already-built binaries through the C<hostperl> and
1943C<hostgenerate> options to Configure.
1944
1945Additionally, if targeting an EBCDIC platform from an ASCII host,
1946or viceversa, you'll need to run Configure with C<-Uhostgenerate>, to
1947indicate that generate_uudmap should be run on the target.
1948
1949Finally, there's also a way of having Configure end early, right after
1950building the host binaries, by cross-compiling without specifying a
1951C<targethost>.
1952
1953The incompatible changes include no longer using xconfig.h, xlib, or
1954Cross.pm, so canned config files and Makefiles will have to be updated.
1955
1956=item *
1957
1958Related to the above, there is now a way of specifying the location of sh
1959(or equivalent) on the target system: C<targetsh>.
1960
1961For example, Android has its sh in /system/bin/sh, so if cross-compiling
1962from a more normal Unixy system with sh in /bin/sh, "targetsh" would end
1963up as /system/bin/sh, and "sh" as /bin/sh.
1964
1965=item *
1966
1967By default, B<gcc> 4.9 does some optimizations that break perl. The B<-fwrapv>
1968option disables those optimizations (and probably others), so for B<gcc> 4.3
1969and later (since the there might be similar problems lurking on older versions
1970too, but B<-fwrapv> was broken before 4.3, and the optimizations probably won't
1971go away), F<Configure> now adds B<-fwrapv> unless the user requests
1972B<-fno-wrapv>, which disables B<-fwrapv>, or B<-fsanitize=undefined>, which
1973turns the overflows B<-fwrapv> ignores into runtime errors.
1974[L<perl #121505|https://rt.perl.org/Public/Bug/Display.html?id=121505>]
1975
1976=back
1977
1978=head1 Testing
1979
1980=over 4
1981
1982=item *
1983
1984The C<test.valgrind> make target now allows tests to be run in parallel.
1985This target allows Perl's test suite to be run under Valgrind, which detects
1986certain sorts of C programming errors, though at significant cost in running
1987time. On suitable hardware, allowing parallel execution claws back a lot of
1988that additional cost. [perl #121431]
1989
1990=item *
1991
1992Various tests in F<t/porting/> are no longer skipped when the perl
1993F<.git> directory is outside the perl tree and pointed to by
1994C<$GIT_DIR>. [perl #120505]
1995
1996=item *
1997
1998The test suite no longer fails when the user's interactive shell maintains a
1999C<$PWD> environment variable, but the F</bin/sh> used for running tests
2000doesn't.
2001
2002=back
2003
2004=head1 Platform Support
2005
2006=head2 New Platforms
2007
2008=over 4
2009
2010=item Android
2011
2012Perl can now be built for Android, either natively or through
2013cross-compilation, for all three currently available architectures (ARM,
2014MIPS, and x86), on a wide range of versions.
2015
2016=item Bitrig
2017
2018Compile support has been added for Bitrig, a fork of OpenBSD.
2019
2020=item FreeMiNT
2021
2022Support has been added for FreeMiNT, a free open-source OS for the Atari ST
2023system and its successors, based on the original MiNT that was officially
2024adopted by Atari.
2025
2026=item Synology
2027
2028Synology ships its NAS boxes with a lean Linux distribution (DSM) on relative
2029cheap CPU's (like the Marvell Kirkwood mv6282 - ARMv5tel or Freescale QorIQ
2030P1022 ppc - e500v2) not meant for workstations or development. These boxes
2031should build now. The basic problems are the non-standard location for tools.
2032
2033=back
2034
2035=head2 Discontinued Platforms
2036
2037=over 4
2038
2039=item C<sfio>
2040
2041Code related to supporting the C<sfio> I/O system has been removed.
2042
2043Perl 5.004 added support to use the native API of C<sfio>, AT&T's Safe/Fast
2044I/O library. This code still built with v5.8.0, albeit with many regression
2045tests failing, but was inadvertently broken before the v5.8.1 release,
2046meaning that it has not worked on any version of Perl released since then.
2047In over a decade we have received no bug reports about this, hence it is clear
2048that no-one is using this functionality on any version of Perl that is still
2049supported to any degree.
2050
2051=item AT&T 3b1
2052
2053Configure support for the 3b1, also known as the AT&T Unix PC (and the similar
2054AT&T 7300), has been removed.
2055
2056=item DG/UX
2057
2058DG/UX was a Unix sold by Data General. The last release was in April 2001.
2059It only runs on Data General's own hardware.
2060
2061=item EBCDIC
2062
2063In the absence of a regular source of smoke reports, code intended to support
2064native EBCDIC platforms will be removed from perl before 5.22.0.
2065
2066=back
2067
2068=head2 Platform-Specific Notes
2069
2070=over 4
2071
2072=item Cygwin
2073
2074=over 4
2075
2076=item *
2077
2078recv() on a connected handle would populate the returned sender
2079address with whatever happened to be in the working buffer. recv()
2080now uses a workaround similar to the Win32 recv() wrapper and returns
2081an empty string when recvfrom(2) doesn't modify the supplied address
2082length. [perl #118843]
2083
2084=item *
2085
2086Fixed a build error in cygwin.c on Cygwin 1.7.28.
2087
2088Tests now handle the errors that occur when C<cygserver> isn't
2089running.
2090
2091=back
2092
2093=item GNU/Hurd
2094
2095The BSD compatibility library C<libbsd> is no longer required for builds.
2096
2097=item Linux
2098
2099The hints file now looks for C<libgdbm_compat> only if C<libgdbm> itself is
2100also wanted. The former is never useful without the latter, and in some
2101circumstances, including it could actually prevent building.
2102
2103=item Mac OS
2104
2105The build system now honors an C<ld> setting supplied by the user running
2106F<Configure>.
2107
2108=item MidnightBSD
2109
2110C<objformat> was removed from version 0.4-RELEASE of MidnightBSD and had been
2111deprecated on earlier versions. This caused the build environment to be
2112erroneously configured for C<a.out> rather than C<elf>. This has been now
2113been corrected.
2114
2115=item Mixed-endian platforms
2116
2117The code supporting C<pack> and C<unpack> operations on mixed endian
2118platforms has been removed. We believe that Perl has long been unable to
2119build on mixed endian architectures (such as PDP-11s), so we don't think
2120that this change will affect any platforms which were able to build v5.18.0.
2121
2122=item VMS
2123
2124=over 4
2125
2126=item *
2127
2128The C<PERL_ENV_TABLES> feature to control the population of %ENV at perl
2129start-up was broken in Perl 5.16.0 but has now been fixed.
2130
2131=item *
2132
2133Skip access checks on remotes in opendir(). [perl #121002]
2134
2135=item *
2136
2137A check for glob metacharacters in a path returned by the
2138L<C<glob()>|perlfunc/glob> operator has been replaced with a check for VMS
2139wildcard characters. This saves a significant number of unnecessary
2140L<C<lstat()>|perlfunc/lstat> calls such that some simple glob operations become
214160-80% faster.
2142
2143=back
2144
2145=item Win32
2146
2147=over 4
2148
2149=item *
2150
2151C<rename> and C<link> on Win32 now set $! to ENOSPC and EDQUOT when
2152appropriate. [perl #119857]
2153
2154=item *
2155
2156The BUILD_STATIC and ALL_STATIC makefile options for linking some or (nearly)
2157all extensions statically (into perl520.dll, and into a separate
2158perl-static.exe too) were broken for MinGW builds. This has now been fixed.
2159
2160The ALL_STATIC option has also been improved to include the Encode and Win32
2161extensions (for both VC++ and MinGW builds).
2162
2163=item *
2164
2165Support for building with Visual C++ 2013 has been added. There are currently
2166two possible test failures (see L<perlwin32/"Testing Perl on Windows">) which
2167will hopefully be resolved soon.
2168
2169=item *
2170
2171Experimental support for building with Intel C++ Compiler has been added. The
2172nmake makefile (win32/Makefile) and the dmake makefile (win32/makefile.mk) can
2173be used. A "nmake test" will not pass at this time due to F<cpan/CGI/t/url.t>.
2174
2175=item *
2176
2177Killing a process tree with L<perlfunc/kill> and a negative signal, was broken
2178starting in 5.18.0. In this bug, C<kill> always returned 0 for a negative
2179signal even for valid PIDs, and no processes were terminated. This has been
2180fixed [perl #121230].
2181
2182=item *
2183
2184The time taken to build perl on Windows has been reduced quite significantly
2185(time savings in the region of 30-40% are typically seen) by reducing the
2186number of, usually failing, I/O calls for each L<C<require()>|perlfunc/require>
2187(for B<miniperl.exe> only).
2188[L<perl #121119|https://rt.perl.org/Public/Bug/Display.html?id=121119>]
2189
2190=item *
2191
2192About 15 minutes of idle sleeping was removed from running C<make test> due to
2193a bug in which the timeout monitor used for tests could not be cancelled once
2194the test completes, and the full timeout period elapsed before running the next
2195test file.
2196[L<perl #121395|https://rt.perl.org/Public/Bug/Display.html?id=121395>]
2197
2198=item *
2199
2200On a perl built without pseudo-fork (pseudo-fork builds were not affected by
2201this bug), killing a process tree with L<C<kill()>|perlfunc/kill> and a negative
2202signal resulted in C<kill()> inverting the returned value. For example, if
2203C<kill()> killed 1 process tree PID then it returned 0 instead of 1, and if
2204C<kill()> was passed 2 invalid PIDs then it returned 2 instead of 0. This has
2205probably been the case since the process tree kill feature was implemented on
2206Win32. It has now been corrected to follow the documented behaviour.
2207[L<perl #121230|https://rt.perl.org/Public/Bug/Display.html?id=121230>]
2208
2209=item *
2210
2211When building a 64-bit perl, an uninitialized memory read in B<miniperl.exe>,
2212used during the build process, could lead to a 4GB B<wperl.exe> being created.
2213This has now been fixed. (Note that B<perl.exe> itself was unaffected, but
2214obviously B<wperl.exe> would have been completely broken.)
2215[L<perl #121471|https://rt.perl.org/Public/Bug/Display.html?id=121471>]
2216
2217=item *
2218
2219Perl can now be built with B<gcc> version 4.8.1 from L<http://www.mingw.org>.
2220This was previously broken due to an incorrect definition of DllMain() in one
2221of perl's source files. Earlier B<gcc> versions were also affected when using
2222version 4 of the w32api package. Versions of B<gcc> available from
2223L<http://mingw-w64.sourceforge.net/> were not affected.
2224[L<perl #121643|https://rt.perl.org/Public/Bug/Display.html?id=121643>]
2225
2226=item *
2227
2228The test harness now has no failures when perl is built on a FAT drive with the
2229Windows OS on an NTFS drive.
2230[L<perl #21442|https://rt.perl.org/Public/Bug/Display.html?id=21442>]
2231
2232=item *
2233
2234When cloning the context stack in fork() emulation, Perl_cx_dup()
2235would crash accessing parameter information for context stack entries
2236that included no parameters, as with C<&foo;>.
2237[L<perl #121721|https://rt.perl.org/Public/Bug/Display.html?id=121721>]
2238
2239=item *
2240
2241Introduced by
2242L<perl #113536|https://rt.perl.org/Public/Bug/Display.html?id=113536>, a memory
2243leak on every call to C<system> and backticks (C< `` >), on most Win32 Perls
2244starting from 5.18.0 has been fixed. The memory leak only occurred if you
2245enabled psuedo-fork in your build of Win32 Perl, and were running that build on
2246Server 2003 R2 or newer OS. The leak does not appear on WinXP SP3.
2247[L<perl #121676|https://rt.perl.org/Public/Bug/Display.html?id=121676>]
2248
2249=back
2250
2251=item WinCE
2252
2253=over 4
2254
2255=item *
2256
2257The building of XS modules has largely been restored. Several still cannot
2258(yet) be built but it is now possible to build Perl on WinCE with only a couple
2259of further patches (to L<Socket> and L<ExtUtils::MakeMaker>), hopefully to be
2260incorporated soon.
2261
2262=item *
2263
2264Perl can now be built in one shot with no user intervention on WinCE by running
2265C<nmake -f Makefile.ce all>.
2266
2267Support for building with EVC (Embedded Visual C++) 4 has been restored. Perl
2268can also be built using Smart Devices for Visual C++ 2005 or 2008.
2269
2270=back
2271
2272=back
2273
2274=head1 Internal Changes
2275
2276=over 4
2277
2278=item *
2279
2280The internal representation has changed for the match variables $1, $2 etc.,
2281$`, $&, $', ${^PREMATCH}, ${^MATCH} and ${^POSTMATCH}. It uses slightly less
2282memory, avoids string comparisons and numeric conversions during lookup, and
2283uses 23 fewer lines of C. This change should not affect any external code.
2284
2285=item *
2286
2287Arrays now use NULL internally to represent unused slots, instead of
2288&PL_sv_undef. &PL_sv_undef is no longer treated as a special value, so
2289av_store(av, 0, &PL_sv_undef) will cause element 0 of that array to hold a
2290read-only undefined scalar. C<$array[0] = anything> will croak and
2291C<\$array[0]> will compare equal to C<\undef>.
2292
2293=item *
2294
2295The SV returned by HeSVKEY_force() now correctly reflects the UTF8ness of the
2296underlying hash key when that key is not stored as a SV. [perl #79074]
2297
2298=item *
2299
2300Certain rarely used functions and macros available to XS code are now
2301deprecated. These are:
2302C<utf8_to_uvuni_buf> (use C<utf8_to_uvchr_buf> instead),
2303C<valid_utf8_to_uvuni> (use C<utf8_to_uvchr_buf> instead),
2304C<NATIVE_TO_NEED> (this did not work properly anyway),
2305and C<ASCII_TO_NEED> (this did not work properly anyway).
2306
2307Starting in this release, almost never does application code need to
2308distinguish between the platform's character set and Latin1, on which the
2309lowest 256 characters of Unicode are based. New code should not use
2310C<utf8n_to_uvuni> (use C<utf8_to_uvchr_buf> instead),
2311nor
2312C<uvuni_to_utf8> (use C<uvchr_to_utf8> instead),
2313
2314=item *
2315
2316The Makefile shortcut targets for many rarely (or never) used testing and
2317profiling targets have been removed, or merged into the only other Makefile
2318target that uses them. Specifically, these targets are gone, along with
2319documentation that referenced them or explained how to use them:
2320
2321 check.third check.utf16 check.utf8 coretest minitest.prep
2322 minitest.utf16 perl.config.dashg perl.config.dashpg
2323 perl.config.gcov perl.gcov perl.gprof perl.gprof.config
2324 perl.pixie perl.pixie.atom perl.pixie.config perl.pixie.irix
2325 perl.third perl.third.config perl.valgrind.config purecovperl
2326 pureperl quantperl test.deparse test.taintwarn test.third
2327 test.torture test.utf16 test.utf8 test_notty.deparse
2328 test_notty.third test_notty.valgrind test_prep.third
2329 test_prep.valgrind torturetest ucheck ucheck.third ucheck.utf16
2330 ucheck.valgrind utest utest.third utest.utf16 utest.valgrind
2331
2332It's still possible to run the relevant commands by "hand" - no underlying
2333functionality has been removed.
2334
2335=item *
2336
2337It is now possible to keep Perl from initializing locale handling.
2338For the most part, Perl doesn't pay attention to locale. (See
2339L<perllocale>.) Nonetheless, until now, on startup, it has always
2340initialized locale handling to the system default, just in case the
2341program being executed ends up using locales. (This is one of the first
2342things a locale-aware program should do, long before Perl knows if it
2343will actually be needed or not.) This works well except when Perl is
2344embedded in another application which wants a locale that isn't the
2345system default. Now, if the environment variable
2346C<PERL_SKIP_LOCALE_INIT> is set at the time Perl is started, this
2347initialization step is skipped. Prior to this, on Windows platforms,
2348the only workaround for this deficiency was to use a hacked-up copy of
2349internal Perl code. Applications that need to use older Perls can
2350discover if the embedded Perl they are using needs the workaround by
2351testing that the C preprocessor symbol C<HAS_SKIP_LOCALE_INIT> is not
2352defined. [RT #38193]
2353
2354=item *
2355
2356C<BmRARE> and C<BmPREVIOUS> have been removed. They were not used anywhere
2357and are not part of the API. For XS modules, they are now #defined as 0.
2358
2359=item *
2360
2361C<sv_force_normal>, which usually croaks on read-only values, used to allow
2362read-only values to be modified at compile time. This has been changed to
2363croak on read-only values regardless. This change uncovered several core
2364bugs.
2365
2366=item *
2367
2368Perl's new copy-on-write mechanism (which is now enabled by default),
2369allows any C<SvPOK> scalar to be automatically upgraded to a copy-on-write
2370scalar when copied. A reference count on the string buffer is stored in
2371the string buffer itself.
2372
2373For example:
2374
2375 $ perl -MDevel::Peek -e'$a="abc"; $b = $a; Dump $a; Dump $b'
2376 SV = PV(0x260cd80) at 0x2620ad8
2377 REFCNT = 1
2378 FLAGS = (POK,IsCOW,pPOK)
2379 PV = 0x2619bc0 "abc"\0
2380 CUR = 3
2381 LEN = 16
2382 COW_REFCNT = 1
2383 SV = PV(0x260ce30) at 0x2620b20
2384 REFCNT = 1
2385 FLAGS = (POK,IsCOW,pPOK)
2386 PV = 0x2619bc0 "abc"\0
2387 CUR = 3
2388 LEN = 16
2389 COW_REFCNT = 1
2390
2391Note that both scalars share the same PV buffer and have a COW_REFCNT
2392greater than zero.
2393
2394This means that XS code which wishes to modify the C<SvPVX()> buffer of an
2395SV should call C<SvPV_force()> or similar first, to ensure a valid (and
2396unshared) buffer, and to call C<SvSETMAGIC()> afterwards. This in fact has
2397always been the case (for example hash keys were already copy-on-write);
2398this change just spreads the COW behaviour to a wider variety of SVs.
2399
2400One important difference is that before 5.18.0, shared hash-key scalars
2401used to have the C<SvREADONLY> flag set; this is no longer the case.
2402
2403This new behaviour can still be disabled by running F<Configure> with
2404B<-Accflags=-DPERL_NO_COW>. This option will probably be removed in Perl
24055.22.
2406
2407=item *
2408
2409C<PL_sawampersand> is now a constant. The switch this variable provided
2410(to enable/disable the pre-match copy depending on whether C<$&> had been
2411seen) has been removed and replaced with copy-on-write, eliminating a few
2412bugs.
2413
2414The previous behaviour can still be enabled by running F<Configure> with
2415B<-Accflags=-DPERL_SAWAMPERSAND>.
2416
2417=item *
2418
2419The functions C<my_swap>, C<my_htonl> and C<my_ntohl> have been removed.
2420It is unclear why these functions were ever marked as I<A>, part of the
2421API. XS code can't call them directly, as it can't rely on them being
2422compiled. Unsurprisingly, no code on CPAN references them.
2423
2424=item *
2425
2426The signature of the C<Perl_re_intuit_start()> regex function has changed;
2427the function pointer C<intuit> in the regex engine plugin structure
2428has also changed accordingly. A new parameter, C<strbeg> has been added;
2429this has the same meaning as the same-named parameter in
2430C<Perl_regexec_flags>. Previously intuit would try to guess the start of
2431the string from the passed SV (if any), and would sometimes get it wrong
2432(e.g. with an overloaded SV).
2433
2434=item *
2435
2436The signature of the C<Perl_regexec_flags()> regex function has
2437changed; the function pointer C<exec> in the regex engine plugin
2438structure has also changed to match. The C<minend> parameter now has
2439type C<SSize_t> to better support 64-bit systems.
2440
2441=item *
2442
2443XS code may use various macros to change the case of a character or code
2444point (for example C<toLOWER_utf8()>). Only a couple of these were
2445documented until now;
2446and now they should be used in preference to calling the underlying
2447functions. See L<perlapi/Character case changing>.
2448
2449=item *
2450
2451The code dealt rather inconsistently with uids and gids. Some
2452places assumed that they could be safely stored in UVs, others
2453in IVs, others in ints. Four new macros are introduced:
2454SvUID(), sv_setuid(), SvGID(), and sv_setgid()
2455
2456=item *
2457
2458C<sv_pos_b2u_flags> has been added to the API. It is similar to C<sv_pos_b2u>,
2459but supports long strings on 64-bit platforms.
2460
2461=item *
2462
2463C<PL_exit_flags> can now be used by perl embedders or other XS code to have
2464perl C<warn> or C<abort> on an attempted exit. [perl #52000]
2465
2466=item *
2467
2468Compiling with C<-Accflags=-PERL_BOOL_AS_CHAR> now allows C99 and C++
2469compilers to emulate the aliasing of C<bool> to C<char> that perl does for
2470C89 compilers. [perl #120314]
2471
2472=item *
2473
2474The C<sv> argument in L<perlapi/sv_2pv_flags>, L<perlapi/sv_2iv_flags>,
2475L<perlapi/sv_2uv_flags>, and L<perlapi/sv_2nv_flags> and their older wrappers
2476sv_2pv, sv_2iv, sv_2uv, sv_2nv, is now non-NULL. Passing NULL now will crash.
2477When the non-NULL marker was introduced en masse in 5.9.3 the functions
2478were marked non-NULL, but since the creation of the SV API in 5.0 alpha 2, if
2479NULL was passed, the functions returned 0 or false-type values. The code that
2480supports C<sv> argument being non-NULL dates to 5.0 alpha 2 directly, and
2481indirectly to Perl 1.0 (pre 5.0 api). The lack of documentation that the
2482functions accepted a NULL C<sv> was corrected in 5.11.0 and between 5.11.0
2483and 5.19.5 the functions were marked NULLOK. As an optimization the NULLOK code
2484has now been removed, and the functions became non-NULL marked again, because
2485core getter-type macros never pass NULL to these functions and would crash
2486before ever passing NULL.
2487
2488The only way a NULL C<sv> can be passed to sv_2*v* functions is if XS code
2489directly calls sv_2*v*. This is unlikely as XS code uses Sv*V* macros to get
2490the underlying value out of the SV. One possible situation which leads to
2491a NULL C<sv> being passed to sv_2*v* functions, is if XS code defines its own
2492getter type Sv*V* macros, which check for NULL B<before> dereferencing and
2493checking the SV's flags through public API Sv*OK* macros or directly using
2494private API C<SvFLAGS>, and if C<sv> is NULL, then calling the sv_2*v functions
2495with a NULL litteral or passing the C<sv> containing a NULL value.
2496
2497=item *
2498
2499newATTRSUB is now a macro
2500
2501The public API newATTRSUB was previously a macro to the private
2502function Perl_newATTRSUB. Function Perl_newATTRSUB has been removed. newATTRSUB
2503is now macro to a different internal function.
2504
2505=item *
2506
2507Changes in warnings raised by C<utf8n_to_uvchr()>
2508
2509This bottom level function decodes the first character of a UTF-8 string
2510into a code point. It is accessible to C<XS> level code, but it's
2511discouraged from using it directly. There are higher level functions
2512that call this that should be used instead, such as
2513L<perlapi/utf8_to_uvchr_buf>. For completeness though, this documents
2514some changes to it. Now, tests for malformations are done before any
2515tests for other potential issues. One of those issues involves code
2516points so large that they have never appeared in any official standard
2517(the current standard has scaled back the highest acceptable code point
2518from earlier versions). It is possible (though not done in CPAN) to
2519warn and/or forbid these code points, while accepting smaller code
2520points that are still above the legal Unicode maximum. The warning
2521message for this now includes the code point if representable on the
2522machine. Previously it always displayed raw bytes, which is what it
2523still does for non-representable code points.
2524
2525=item *
2526
2527Regexp engine changes that affect the pluggable regex engine interface
2528
2529Many flags that used to be exposed via regexp.h and used to populate the
2530extflags member of struct regexp have been removed. These fields were
2531technically private to Perl's own regexp engine and should not have been
2532exposed there in the first place.
2533
2534The affected flags are:
2535
2536 RXf_NOSCAN
2537 RXf_CANY_SEEN
2538 RXf_GPOS_SEEN
2539 RXf_GPOS_FLOAT
2540 RXf_ANCH_BOL
2541 RXf_ANCH_MBOL
2542 RXf_ANCH_SBOL
2543 RXf_ANCH_GPOS
2544
2545As well as the follow flag masks:
2546
2547 RXf_ANCH_SINGLE
2548 RXf_ANCH
2549
2550All have been renamed to PREGf_ equivalents and moved to regcomp.h.
2551
2552The behavior previously achieved by setting one or more of the RXf_ANCH_
2553flags (via the RXf_ANCH mask) have now been replaced by a *single* flag bit
2554in extflags:
2555
2556 RXf_IS_ANCHORED
2557
2558pluggable regex engines which previously used to set these flags should
2559now set this flag ALONE.
2560
2561=item *
2562
2563The Perl core now consistently uses C<av_tindex()> ("the top index of an
2564array") as a more clearly-named synonym for C<av_len()>.
2565
2566=item *
2567
2568The obscure interpreter variable C<PL_timesbuf> is expected to be removed
2569early in the 5.21.x development series, so that Perl 5.22.0 will not provide
2570it to XS authors. While the variable still exists in 5.20.0, we hope that
2571this advance warning of the deprecation will help anyone who is using that
2572variable.
2573
2574=back
2575
2576=head1 Selected Bug Fixes
2577
2578=head2 Regular Expressions
2579
2580=over 4
2581
2582=item *
2583
2584Fixed a small number of regexp constructions that could either fail to
2585match or crash perl when the string being matched against was
2586allocated above the 2GB line on 32-bit systems. [RT #118175]
2587
2588=item *
2589
2590Various memory leaks involving the parsing of the C<(?[...])> regular
2591expression construct have been fixed.
2592
2593=item *
2594
2595C<(?[...])> now allows interpolation of precompiled patterns consisting of
2596C<(?[...])> with bracketed character classes inside (C<$pat =
2597S<qr/(?[ [a] ])/;> S</(?[ $pat ])/>>). Formerly, the brackets would
2598confuse the regular expression parser.
2599
2600=item *
2601
2602The "Quantifier unexpected on zero-length expression" warning message could
2603appear twice starting in Perl v5.10 for a regular expression also
2604containing alternations (e.g., "a|b") triggering the trie optimisation.
2605
2606=item *
2607
2608Perl v5.18 inadvertently introduced a bug whereby interpolating mixed up-
2609and down-graded UTF-8 strings in a regex could result in malformed UTF-8
2610in the pattern: specifically if a downgraded character in the range
2611C<\x80..\xff> followed a UTF-8 string, e.g.
2612
2613 utf8::upgrade( my $u = "\x{e5}");
2614 utf8::downgrade(my $d = "\x{e5}");
2615 /$u$d/
2616
2617[RT #118297]
2618
2619=item *
2620
2621In regular expressions containing multiple code blocks, the values of
2622C<$1>, C<$2>, etc., set by nested regular expression calls would leak from
2623one block to the next. Now these variables always refer to the outer
2624regular expression at the start of an embedded block [perl #117917].
2625
2626=item *
2627
2628C</$qr/p> was broken in Perl 5.18.0; the C</p> flag was ignored. This has been
2629fixed. [perl #118213]
2630
2631=item *
2632
2633Starting in Perl 5.18.0, a construct like C</[#](?{})/x> would have its C<#>
2634incorrectly interpreted as a comment. The code block would be skipped,
2635unparsed. This has been corrected.
2636
2637=item *
2638
2639Starting in Perl 5.001, a regular expression like C</[#$a]/x> or C</[#]$a/x>
2640would have its C<#> incorrectly interpreted as a comment, so the variable would
2641not interpolate. This has been corrected. [perl #45667]
2642
2643=item *
2644
2645Perl 5.18.0 inadvertently made dereferenced regular expressions
2646S<(C<${ qr// }>)> false as booleans. This has been fixed.
2647
2648=item *
2649
2650The use of C<\G> in regular expressions, where it's not at the start of the
2651pattern, is now slightly less buggy (although it is still somewhat
2652problematic).
2653
2654=item *
2655
2656Where a regular expression included code blocks (C</(?{...})/>), and where the
2657use of constant overloading triggered a re-compilation of the code block, the
2658second compilation didn't see its outer lexical scope. This was a regression
2659in Perl 5.18.0.
2660
2661=item *
2662
2663The string position set by C<pos> could shift if the string changed
2664representation internally to or from utf8. This could happen, e.g., with
2665references to objects with string overloading.
2666
2667=item *
2668
2669Taking references to the return values of two C<pos> calls with the same
2670argument, and then assigning a reference to one and C<undef> to the other,
2671could result in assertion failures or memory leaks.
2672
2673=item *
2674
2675Elements of @- and @+ now update correctly when they refer to non-existent
2676captures. Previously, a referenced element (C<$ref = \$-[1]>) could refer to
2677the wrong match after subsequent matches.
2678
2679=item *
2680
2681The code that parses regex backrefs (or ambiguous backref/octals) such as \123
2682did a simple atoi(), which could wrap round to negative values on long digit
2683strings and cause segmentation faults. This has now been fixed. [perl
2684#119505]
2685
2686=item *
2687
2688Assigning another typeglob to C<*^R> no longer makes the regular expression
2689engine crash.
2690
2691=item *
2692
2693The C<\N> regular expression escape, when used without the curly braces (to
2694mean C<[^\n]>), was ignoring a following C<*> if followed by whitespace
2695under /x. It had been this way since C<\N> to mean C<[^\n]> was introduced
2696in 5.12.0.
2697
2698=item *
2699
2700C<s///>, C<tr///> and C<y///> now work when a wide character is used as the
2701delimiter. [perl #120463]
2702
2703=item *
2704
2705Some cases of unterminated (?...) sequences in regular expressions (e.g.,
2706C</(?</>) have been fixed to produce the proper error message instead of
2707"panic: memory wrap". Other cases (e.g., C</(?(/>) have yet to be fixed.
2708
2709=item *
2710
2711When a reference to a reference to an overloaded object was returned from
2712a regular expression C<(??{...})> code block, an incorrect implicit
2713dereference could take place if the inner reference had been returned by
2714a code block previously.
2715
2716=item *
2717
2718A tied variable returned from C<(??{...})> sees the inner values of match
2719variables (i.e., the $1 etc. from any matches inside the block) in its
2720FETCH method. This was not the case if a reference to an overloaded object
2721was the last thing assigned to the tied variable. Instead, the match
2722variables referred to the outer pattern during the FETCH call.
2723
2724=item *
2725
2726Fix unexpected tainting via regexp using locale. Previously, under certain
2727conditions, the use of character classes could cause tainting when it
2728shouldn't. Some character classes are locale-dependent, but before this
2729patch, sometimes tainting was happening even for character classes that
2730don't depend on the locale. [perl #120675]
2731
2732=item *
2733
2734Under certain conditions, Perl would throw an error if in an lookbehind
2735assertion in a regexp, the assertion referred to a named subpattern,
2736complaining the lookbehind was variable when it wasn't. This has been
2737fixed. [perl #120600], [perl #120618]. The current fix may be improved
2738on in the future.
2739
2740=item *
2741
2742C<$^R> wasn't available outside of the regular expression that
2743initialized it. [perl #121070]
2744
2745=item *
2746
2747A large set of fixes and refactoring for re_intuit_start() was merged,
2748the highlights are:
2749
2750=over
2751
2752=item *
2753
2754Fixed a panic when compiling the regular expression
2755C</\x{100}[xy]\x{100}{2}/>.
2756
2757=item *
2758
2759Fixed a performance regression when performing a global pattern match
2760against a UTF-8 string. [perl #120692]
2761
2762=item *
2763
2764Fixed another performance issue where matching a regular expression
2765like C</ab.{1,2}x/> against a long UTF-8 string would unnecessarily
2766calculate byte offsets for a large portion of the string. [perl
2767#120692]
2768
2769=back
2770
2771=item *
2772
2773Fixed an alignment error when compiling regular expressions when built
2774with GCC on HP-UX 64-bit.
2775
2776=item *
2777
2778On 64-bit platforms C<pos> can now be set to a value higher than 2**31-1.
2779[perl #72766]
2780
2781=back
2782
2783=head2 Perl 5 Debugger and -d
2784
2785=over 4
2786
2787=item *
2788
2789The debugger's C<man> command been fixed. It was broken in the v5.18.0
2790release. The C<man> command is aliased to the names C<doc> and C<perldoc> -
2791all now work again.
2792
2793=item *
2794
2795C<@_> is now correctly visible in the debugger, fixing a regression
2796introduced in v5.18.0's debugger. [RT #118169]
2797
2798=item *
2799
2800Under copy-on-write builds (the default as of 5.20.0) C<< ${'_<-e'}[0] >>
2801no longer gets mangled. This is the first line of input saved for the
2802debugger's use for one-liners [perl #118627].
2803
2804=item *
2805
2806On non-threaded builds, setting C<${"_E<lt>filename"}> to a reference or
2807typeglob no longer causes C<__FILE__> and some error messages to produce a
2808corrupt string, and no longer prevents C<#line> directives in string evals from
2809providing the source lines to the debugger. Threaded builds were unaffected.
2810
2811=item *
2812
2813Starting with Perl 5.12, line numbers were off by one if the B<-d> switch was
2814used on the #! line. Now they are correct.
2815
2816=item *
2817
2818C<*DB::DB = sub {} if 0> no longer stops Perl's debugging mode from finding
2819C<DB::DB> subs declared thereafter.
2820
2821=item *
2822
2823C<%{'_<...'}> hashes now set breakpoints on the corresponding C<@{'_<...'}>
2824rather than whichever array C<@DB::dbline> is aliased to. [perl #119799]
2825
2826=item *
2827
2828Call set-magic when setting $DB::sub. [perl #121255]
2829
2830=item *
2831
2832The debugger's "n" command now respects lvalue subroutines and steps over
2833them [perl #118839].
2834
2835=back
2836
2837=head2 Lexical Subroutines
2838
2839=over 4
2840
2841=item *
2842
2843Lexical constants (C<my sub a() { 42 }>) no longer crash when inlined.
2844
2845=item *
2846
2847Parameter prototypes attached to lexical subroutines are now respected when
2848compiling sub calls without parentheses. Previously, the prototypes were
2849honoured only for calls I<with> parentheses. [RT #116735]
2850
2851=item *
2852
2853Syntax errors in lexical subroutines in combination with calls to the same
2854subroutines no longer cause crashes at compile time.
2855
2856=item *
2857
2858Deep recursion warnings no longer crash lexical subroutines. [RT #118521]
2859
2860=item *
2861
2862The dtrace sub-entry probe now works with lexical subs, instead of
2863crashing [perl #118305].
2864
2865=item *
2866
2867Undefining an inlinable lexical subroutine (C<my sub foo() { 42 } undef
2868&foo>) would result in a crash if warnings were turned on.
2869
2870=item *
2871
2872An undefined lexical sub used as an inherited method no longer crashes.
2873
2874=item *
2875
2876The presence of a lexical sub named "CORE" no longer stops the CORE::
2877prefix from working.
2878
2879=back
2880
2881=head2 Everything Else
2882
2883=over 4
2884
2885=item *
2886
2887The OP allocation code now returns correctly aligned memory in all cases
2888for C<struct pmop>. Previously it could return memory only aligned to a
28894-byte boundary, which is not correct for an ithreads build with 64 bit IVs
2890on some 32 bit platforms. Notably, this caused the build to fail completely
2891on sparc GNU/Linux. [RT #118055]
2892
2893=item *
2894
2895Evaluating large hashes in scalar context is now much faster, as the number
2896of used chains in the hash is now cached for larger hashes. Smaller hashes
2897continue not to store it and calculate it when needed, as this saves one IV.
2898That would be 1 IV overhead for every object built from a hash. [RT #114576]
2899
2900=item *
2901
2902Perl v5.16 inadvertently introduced a bug whereby calls to XSUBs that were
2903not visible at compile time were treated as lvalues and could be assigned
2904to, even when the subroutine was not an lvalue sub. This has been fixed.
2905[RT #117947]
2906
2907=item *
2908
2909In Perl v5.18.0 dualvars that had an empty string for the string part but a
2910non-zero number for the number part starting being treated as true. In
2911previous versions they were treated as false, the string representation
2912taking precedeence. The old behaviour has been restored. [RT #118159]
2913
2914=item *
2915
2916Since Perl v5.12, inlining of constants that override built-in keywords of
2917the same name had countermanded C<use subs>, causing subsequent mentions of
2918the constant to use the built-in keyword instead. This has been fixed.
2919
2920=item *
2921
2922The warning produced by C<-l $handle> now applies to IO refs and globs, not
2923just to glob refs. That warning is also now UTF8-clean. [RT #117595]
2924
2925=item *
2926
2927C<delete local $ENV{nonexistent_env_var}> no longer leaks memory.
2928
2929=item *
2930
2931C<sort> and C<require> followed by a keyword prefixed with C<CORE::> now
2932treat it as a keyword, and not as a subroutine or module name. [RT #24482]
2933
2934=item *
2935
2936Through certain conundrums, it is possible to cause the current package to
2937be freed. Certain operators (C<bless>, C<reset>, C<open>, C<eval>) could
2938not cope and would crash. They have been made more resilient. [RT #117941]
2939
2940=item *
2941
2942Aliasing filehandles through glob-to-glob assignment would not update
2943internal method caches properly if a package of the same name as the
2944filehandle existed, resulting in filehandle method calls going to the
2945package instead. This has been fixed.
2946
2947=item *
2948
2949C<./Configure -de -Dusevendorprefix> didn't default. [RT #64126]
2950
2951=item *
2952
2953The C<Statement unlikely to be reached> warning was listed in
2954L<perldiag> as an C<exec>-category warning, but was enabled and disabled
2955by the C<syntax> category. On the other hand, the C<exec> category
2956controlled its fatal-ness. It is now entirely handled by the C<exec>
2957category.
2958
2959=item *
2960
2961The "Replacement list is longer that search list" warning for C<tr///> and
2962C<y///> no longer occurs in the presence of the C</c> flag. [RT #118047]
2963
2964=item *
2965
2966Stringification of NVs are not cached so that the lexical locale controls
2967stringification of the decimal point. [perl #108378] [perl #115800]
2968
2969=item *
2970
2971There have been several fixes related to Perl's handling of locales. perl
2972#38193 was described above in L</Internal Changes>.
2973Also fixed is
2974#118197, where the radix (decimal point) character had to be an ASCII
2975character (which doesn't work for some non-Western languages);
2976and #115808, in which C<POSIX::setlocale()> on failure returned an
2977C<undef> which didn't warn about not being defined even if those
2978warnings were enabled.
2979
2980=item *
2981
2982Compiling a C<split> operator whose third argument is a named constant
d5921089 2983evaluating to 0 no longer causes the constant's value to change.
238894db
RS
2984
2985=item *
2986
2987A named constant used as the second argument to C<index> no longer gets
2988coerced to a string if it is a reference, regular expression, dualvar, etc.
2989
2990=item *
2991
2992A named constant evaluating to the undefined value used as the second
2993argument to C<index> no longer produces "uninitialized" warnings at compile
2994time. It will still produce them at run time.
2995
2996=item *
2997
2998When a scalar was returned from a subroutine in @INC, the referenced scalar
2999was magically converted into an IO thingy, possibly resulting in "Bizarre
3000copy" errors if that scalar continued to be used elsewhere. Now Perl uses
3001an internal copy of the scalar instead.
3002
3003=item *
3004
3005Certain uses of the C<sort> operator are optimised to modify an array in
3006place, such as C<@a = sort @a>. During the sorting, the array is made
3007read-only. If a sort block should happen to die, then the array remained
3008read-only even outside the C<sort>. This has been fixed.
3009
3010=item *
3011
3012C<$a> and C<$b> inside a sort block are aliased to the actual arguments to
3013C<sort>, so they can be modified through those two variables. This did not
3014always work, e.g., for lvalue subs and C<$#ary>, and probably many other
3015operators. It works now.
3016
3017=item *
3018
3019The arguments to C<sort> are now all in list context. If the C<sort>
3020itself were called in void or scalar context, then I<some>, but not all, of
3021the arguments used to be in void or scalar context.
3022
3023=item *
3024
3025Subroutine prototypes with Unicode characters above U+00FF were getting
3026mangled during closure cloning. This would happen with subroutines closing
3027over lexical variables declared outside, and with lexical subs.
3028
3029=item *
3030
3031C<UNIVERSAL::can> now treats its first argument the same way that method
3032calls do: Typeglobs and glob references with non-empty IO slots are treated
3033as handles, and strings are treated as filehandles, rather than packages,
3034if a handle with that name exists [perl #113932].
3035
3036=item *
3037
3038Method calls on typeglobs (e.g., C<< *ARGV->getline >>) used to stringify
3039the typeglob and then look it up again. Combined with changes in Perl
30405.18.0, this allowed C<< *foo->bar >> to call methods on the "foo" package
3041(like C<< foo->bar >>). In some cases it could cause the method to be
3042called on the wrong handle. Now a typeglob argument is treated as a
3043handle (just like C<< (\*foo)->bar >>), or, if its IO slot is empty, an
3044error is raised.
3045
3046=item *
3047
3048Assigning a vstring to a tied variable or to a subroutine argument aliased
3049to a nonexistent hash or array element now works, without flattening the
3050vstring into a regular string.
3051
3052=item *
3053
3054C<pos>, C<tie>, C<tied> and C<untie> did not work
3055properly on subroutine arguments aliased to nonexistent
3056hash and array elements [perl #77814, #27010].
3057
3058=item *
3059
3060The C<< => >> fat arrow operator can now quote built-in keywords even if it
3061occurs on the next line, making it consistent with how it treats other
3062barewords.
3063
3064=item *
3065
3066Autovivifying a subroutine stub via C<\&$glob> started causing crashes in Perl
30675.18.0 if the $glob was merely a copy of a real glob, i.e., a scalar that had
3068had a glob assigned to it. This has been fixed. [perl #119051]
3069
3070=item *
3071
3072Perl used to leak an implementation detail when it came to referencing the
3073return values of certain operators. C<for ($a+$b) { warn \$_; warn \$_ }> used
3074to display two different memory addresses, because the C<\> operator was
3075copying the variable. Under threaded builds, it would also happen for
3076constants (C<for(1) { ... }>). This has been fixed. [perl #21979, #78194,
3077#89188, #109746, #114838, #115388]
3078
3079=item *
3080
3081The range operator C<..> was returning the same modifiable scalars with each
3082call, unless it was the only thing in a C<foreach> loop header. This meant
3083that changes to values within the list returned would be visible the next time
3084the operator was executed. [perl #3105]
3085
3086=item *
3087
3088Constant folding and subroutine inlining no longer cause operations that would
3089normally return new modifiable scalars to return read-only values instead.
3090
3091=item *
3092
3093Closures of the form C<sub () { $some_variable }> are no longer inlined,
3094causing changes to the variable to be ignored by callers of the subroutine.
3095[perl #79908]
3096
3097=item *
3098
3099Return values of certain operators such as C<ref> would sometimes be shared
3100between recursive calls to the same subroutine, causing the inner call to
3101modify the value returned by C<ref> in the outer call. This has been fixed.
3102
3103=item *
3104
3105C<__PACKAGE__> and constants returning a package name or hash key are now
3106consistently read-only. In various previous Perl releases, they have become
3107mutable under certain circumstances.
3108
3109=item *
3110
3111Enabling "used once" warnings no longer causes crashes on stash circularities
3112created at compile time (C<*Foo::Bar::Foo:: = *Foo::>).
3113
3114=item *
3115
3116Undef constants used in hash keys (C<use constant u =E<gt> undef; $h{+u}>) no
3117longer produce "uninitialized" warnings at compile time.
3118
3119=item *
3120
3121Modifying a substitution target inside the substitution replacement no longer
3122causes crashes.
3123
3124=item *
3125
3126The first statement inside a string eval used to use the wrong pragma setting
3127sometimes during constant folding. C<eval 'uc chr 0xe0'> would randomly choose
3128between Unicode, byte, and locale semantics. This has been fixed.
3129
3130=item *
3131
3132The handling of return values of @INC filters (subroutines returned by
3133subroutines in @INC) has been fixed in various ways. Previously tied variables
3134were mishandled, and setting $_ to a reference or typeglob could result in
3135crashes.
3136
3137=item *
3138
3139The C<SvPVbyte> XS function has been fixed to work with tied scalars returning
3140something other than a string. It used to return utf8 in those cases where
3141C<SvPV> would.
3142
3143=item *
3144
3145Perl 5.18.0 inadvertently made C<--> and C<++> crash on dereferenced regular
3146expressions, and stopped C<++> from flattening vstrings.
3147
3148=item *
3149
3150C<bless> no longer dies with "Can't bless non-reference value" if its first
3151argument is a tied reference.
3152
3153=item *
3154
3155C<reset> with an argument no longer skips copy-on-write scalars, regular
3156expressions, typeglob copies, and vstrings. Also, when encountering those or
3157read-only values, it no longer skips any array or hash with the same name.
3158
3159=item *
3160
3161C<reset> with an argument now skips scalars aliased to typeglobs
3162(C<for $z (*foo) { reset "z" }>). Previously it would corrupt memory or crash.
3163
3164=item *
3165
3166C<ucfirst> and C<lcfirst> were not respecting the bytes pragma. This was a
3167regression from Perl 5.12. [perl #117355]
3168
3169=item *
3170
3171Changes to C<UNIVERSAL::DESTROY> now update DESTROY caches in all classes,
3172instead of causing classes that have already had objects destroyed to continue
3173using the old sub. This was a regression in Perl 5.18. [perl #114864]
3174
3175=item *
3176
3177All known false-positive occurrences of the deprecation warning "Useless use of
3178'\'; doesn't escape metacharacter '%c'", added in Perl 5.18.0, have been
3179removed. [perl #119101]
3180
3181=item *
3182
3183The value of $^E is now saved across signal handlers on Windows. [perl #85104]
3184
3185=item *
3186
3187A lexical filehandle (as in C<open my $fh...>) is usually given a name based on
3188the current package and the name of the variable, e.g. "main::$fh". Under
3189recursion, the filehandle was losing the "$fh" part of the name. This has been
3190fixed.
3191
3192=item *
3193
3194Uninitialized values returned by XSUBs are no longer exempt from uninitialized
3195warnings. [perl #118693]
3196
3197=item *
3198
3199C<elsif ("")> no longer erroneously produces a warning about void context.
3200[perl #118753]
3201
3202=item *
3203
3204Passing C<undef> to a subroutine now causes @_ to contain the same read-only
3205undefined scalar that C<undef> returns. Furthermore, C<exists $_[0]> will now
3206return true if C<undef> was the first argument. [perl #7508, #109726]
3207
3208=item *
3209
3210Passing a non-existent array element to a subroutine does not usually
3211autovivify it unless the subroutine modifies its argument. This did not work
3212correctly with negative indices and with non-existent elements within the
3213array. The element would be vivified immediately. The delayed vivification
3214has been extended to work with those. [perl #118691]
3215
3216=item *
3217
3218Assigning references or globs to the scalar returned by $#foo after the @foo
3219array has been freed no longer causes assertion failures on debugging builds
3220and memory leaks on regular builds.
3221
3222=item *
3223
3224On 64-bit platforms, large ranges like 1..1000000000000 no longer crash, but
3225eat up all your memory instead. [perl #119161]
3226
3227=item *
3228
3229C<__DATA__> now puts the C<DATA> handle in the right package, even if the
3230current package has been renamed through glob assignment.
3231
3232=item *
3233
3234When C<die>, C<last>, C<next>, C<redo>, C<goto> and C<exit> unwind the scope,
3235it is possible for C<DESTROY> recursively to call a subroutine or format that
3236is currently being exited. It that case, sometimes the lexical variables
3237inside the sub would start out having values from the outer call, instead of
3238being undefined as they should. This has been fixed. [perl #119311]
3239
3240=item *
3241
3242${^MPEN} is no longer treated as a synonym for ${^MATCH}.
3243
3244=item *
3245
3246Perl now tries a little harder to return the correct line number in
3247C<(caller)[2]>. [perl #115768]
3248
3249=item *
3250
3251Line numbers inside multiline quote-like operators are now reported correctly.
3252[perl #3643]
3253
3254=item *
3255
3256C<#line> directives inside code embedded in quote-like operators are now
3257respected.
3258
3259=item *
3260
3261Line numbers are now correct inside the second here-doc when two here-doc
3262markers occur on the same line.
3263
3264=item *
3265
3266An optimization in Perl 5.18 made incorrect assumptions causing a bad
3267interaction with the L<Devel::CallParser> CPAN module. If the module was
3268loaded then lexical variables declared in separate statements following a
3269C<my(...)> list might fail to be cleared on scope exit.
3270
3271=item *
3272
3273C<&xsub> and C<goto &xsub> calls now allow the called subroutine to autovivify
3274elements of @_.
3275
3276=item *
3277
3278C<&xsub> and C<goto &xsub> no longer crash if *_ has been undefined and has no
3279ARRAY entry (i.e. @_ does not exist).
3280
3281=item *
3282
3283C<&xsub> and C<goto &xsub> now work with tied @_.
3284
3285=item *
3286
3287Overlong identifiers no longer cause a buffer overflow (and a crash). They
3288started doing so in Perl 5.18.
3289
3290=item *
3291
3292The warning "Scalar value @hash{foo} better written as $hash{foo}" now produces
3293far fewer false positives. In particular, C<@hash{+function_returning_a_list}>
3294and C<@hash{ qw "foo bar baz" }> no longer warn. The same applies to array
3295slices. [perl #28380, #114024]
3296
3297=item *
3298
3299C<$! = EINVAL; waitpid(0, WNOHANG);> no longer goes into an internal infinite
3300loop. [perl #85228]
3301
3302=item *
3303
3304A possible segmentation fault in filehandle duplication has been fixed.
3305
3306=item *
3307
3308A subroutine in @INC can return a reference to a scalar containing the initial
3309contents of the file. However, that scalar was freed prematurely if not
3310referenced elsewhere, giving random results.
3311
3312=item *
3313
3314C<last> no longer returns values that the same statement has accumulated so
3315far, fixing amongst other things the long-standing bug that C<push @a, last>
3316would try to return the @a, copying it like a scalar in the process and
3317resulting in the error, "Bizarre copy of ARRAY in last." [perl #3112]
3318
3319=item *
3320
3321In some cases, closing file handles opened to pipe to or from a process, which
3322had been duplicated into a standard handle, would call perl's internal waitpid
3323wrapper with a pid of zero. With the fix for [perl #85228] this zero pid was
3324passed to C<waitpid>, possibly blocking the process. This wait for process
3325zero no longer occurs. [perl #119893]
3326
3327=item *
3328
3329C<select> used to ignore magic on the fourth (timeout) argument, leading to
3330effects such as C<select> blocking indefinitely rather than the expected sleep
3331time. This has now been fixed. [perl #120102]
3332
3333=item *
3334
3335The class name in C<for my class $foo> is now parsed correctly. In the case of
3336the second character of the class name being followed by a digit (e.g. 'a1b')
3337this used to give the error "Missing $ on loop variable". [perl #120112]
3338
3339=item *
3340
3341Perl 5.18.0 accidentally disallowed C<-bareword> under C<use strict> and
3342C<use integer>. This has been fixed. [perl #120288]
3343
3344=item *
3345
3346C<-a> at the start of a line (or a hyphen with any single letter that is
3347not a filetest operator) no longer produces an erroneous 'Use of "-a"
3348without parentheses is ambiguous' warning. [perl #120288]
3349
3350=item *
3351
3352Lvalue context is now properly propagated into bare blocks and C<if> and
3353C<else> blocks in lvalue subroutines. Previously, arrays and hashes would
3354sometimes incorrectly be flattened when returned in lvalue list context, or
3355"Bizarre copy" errors could occur. [perl #119797]
3356
3357=item *
3358
3359Lvalue context is now propagated to the branches of C<||> and C<&&> (and
3360their alphabetic equivalents, C<or> and C<and>). This means
3361C<foreach (pos $x || pos $y) {...}> now allows C<pos> to be modified
3362through $_.
3363
3364=item *
3365
3366C<stat> and C<readline> remember the last handle used; the former
3367for the special C<_> filehandle, the latter for C<${^LAST_FH}>.
3368C<eval "*foo if 0"> where *foo was the last handle passed to C<stat>
3369or C<readline> could cause that handle to be forgotten if the
3370handle were not opened yet. This has been fixed.
3371
3372=item *
3373
3374Various cases of C<delete $::{a}>, C<delete $::{ENV}> etc. causing a crash
3375have been fixed. [perl #54044]
3376
3377=item *
3378
3379Setting C<$!> to EACCESS before calling C<require> could affect
3380C<require>'s behaviour. This has been fixed.
3381
3382=item *
3383
3384The "Can't use \1 to mean $1 in expression" warning message now only occurs
3385on the right-hand (replacement) part of a substitution. Formerly it could
3386happen in code embedded in the left-hand side, or in any other quote-like
3387operator.
3388
3389=item *
3390
3391Blessing into a reference (C<bless $thisref, $thatref>) has long been
3392disallowed, but magical scalars for the second like C<$/> and those tied
3393were exempt. They no longer are. [perl #119809]
3394
3395=item *
3396
3397Blessing into a reference was accidentally allowed in 5.18 if the class
3398argument were a blessed reference with stale method caches (i.e., whose
3399class had had subs defined since the last method call). They are
3400disallowed once more, as in 5.16.
3401
3402=item *
3403
3404C<< $x->{key} >> where $x was declared as C<my Class $x> no longer crashes
3405if a Class::FIELDS subroutine stub has been declared.
3406
3407=item *
3408
3409C<@$obj{'key'}> and C<${$obj}{key}> used to be exempt from compile-time
3410field checking ("No such class field"; see L<fields>) but no longer are.
3411
3412=item *
3413
3414A nonexistent array element with a large index passed to a subroutine that
3415ties the array and then tries to access the element no longer results in a
3416crash.
3417
3418=item *
3419
3420Declaring a subroutine stub named NEGATIVE_INDICES no longer makes negative
3421array indices crash when the current package is a tied array class.
3422
3423=item *
3424
3425Declaring a C<require>, C<glob>, or C<do> subroutine stub in the
3426CORE::GLOBAL:: package no longer makes compilation of calls to the
3427corresponding functions crash.
3428
3429=item *
3430
3431Aliasing CORE::GLOBAL:: functions to constants stopped working in Perl 5.10
3432but has now been fixed.
3433
3434=item *
3435
3436When C<`...`> or C<qx/.../> calls a C<readpipe> override, double-quotish
3437interpolation now happens, as is the case when there is no override.
3438Previously, the presence of an override would make these quote-like
3439operators act like C<q{}>, suppressing interpolation. [perl #115330]
3440
3441=item *
3442
3443C<<<<`...`> here-docs (with backticks as the delimiters) now call
3444C<readpipe> overrides. [perl #119827]
3445
3446=item *
3447
3448C<&CORE::exit()> and C<&CORE::die()> now respect L<vmsish> hints.
3449
3450=item *
3451
3452Undefining a glob that triggers a DESTROY method that undefines the same
3453glob is now safe. It used to produce "Attempt to free unreferenced glob
3454pointer" warnings and leak memory.
3455
3456=item *
3457
3458If subroutine redefinition (C<eval 'sub foo{}'> or C<newXS> for XS code)
3459triggers a DESTROY method on the sub that is being redefined, and that
3460method assigns a subroutine to the same slot (C<*foo = sub {}>), C<$_[0]>
3461is no longer left pointing to a freed scalar. Now DESTROY is delayed until
3462the new subroutine has been installed.
3463
3464=item *
3465
3466On Windows, perl no longer calls CloseHandle() on a socket handle. This makes
3467debugging easier on Windows by removing certain irrelevant bad handle
3468exceptions. It also fixes a race condition that made socket functions randomly
3469fail in a Perl process with multiple OS threads, and possible test failures in
3470F<dist/IO/t/cachepropagate-tcp.t>. [perl #120091/118059]
3471
3472=item *
3473
3474Formats involving UTF-8 encoded strings, or strange vars like ties,
3475overloads, or stringified refs (and in recent
3476perls, pure NOK vars) would generally do the wrong thing in formats
3477when the var is treated as a string and repeatedly chopped, as in
3478C<< ^<<<~~ >> and similar. This has now been resolved.
3479[perl #33832/45325/113868/119847/119849/119851]
3480
3481=item *
3482
3483C<< semctl(..., SETVAL, ...) >> would set the semaphore to the top
348432-bits of the supplied integer instead of the bottom 32-bits on
348564-bit big-endian systems. [perl #120635]
3486
3487=item *
3488
3489C<< readdir() >> now only sets C<$!> on error. C<$!> is no longer set
3490to C<EBADF> when then terminating C<undef> is read from the directory
3491unless the system call sets C<$!>. [perl #118651]
3492
3493=item *
3494
3495C<&CORE::glob> no longer causes an intermittent crash due to perl's stack
3496getting corrupted. [perl #119993]
3497
3498=item *
3499
3500C<open> with layers that load modules (e.g., "<:encoding(utf8)") no longer
3501runs the risk of crashing due to stack corruption.
3502
3503=item *
3504
3505Perl 5.18 broke autoloading via C<< ->SUPER::foo >> method calls by looking
3506up AUTOLOAD from the current package rather than the current package's
3507superclass. This has been fixed. [perl #120694]
3508
3509=item *
3510
3511A longstanding bug causing C<do {} until CONSTANT>, where the constant
3512holds a true value, to read unallocated memory has been resolved. This
3513would usually happen after a syntax error. In past versions of Perl it has
3514crashed intermittently. [perl #72406]
3515
3516=item *
3517
3518Fix HP-UX C<$!> failure. HP-UX strerror() returns an empty string for an
3519unknown error code. This caused an assertion to fail under DEBUGGING
3520builds. Now instead, the returned string for C<"$!"> contains text
3521indicating the code is for an unknown error.
3522
3523=item *
3524
3525Individually-tied elements of @INC (as in C<tie $INC[0]...>) are now
3526handled correctly. Formerly, whether a sub returned by such a tied element
3527would be treated as a sub depended on whether a FETCH had occurred
3528previously.
3529
3530=item *
3531
3532C<getc> on a byte-sized handle after the same C<getc> operator had been
3533used on a utf8 handle used to treat the bytes as utf8, resulting in erratic
3534behavior (e.g., malformed UTF-8 warnings).
3535
3536=item *
3537
3538An initial C<{> at the beginning of a format argument line was always
3539interpreted as the beginning of a block prior to v5.18. In Perl v5.18, it
3540started being treated as an ambiguous token. The parser would guess
3541whether it was supposed to be an anonymous hash constructor or a block
3542based on the contents. Now the previous behavious has been restored.
3543[perl #119973]
3544
3545=item *
3546
3547In Perl v5.18 C<undef *_; goto &sub> and C<local *_; goto &sub> started
3548crashing. This has been fixed. [perl #119949]
3549
3550=item *
3551
3552Backticks (C< `` > or C< qx// >) combined with multiple threads on
3553Win32 could result in output sent to stdout on one thread being
3554captured by backticks of an external command in another thread.
3555
3556This could occur for pseudo-forked processes too, as Win32's
3557pseudo-fork is implemented in terms of threads. [perl #77672]
3558
3559=item *
3560
3561C<< open $fh, ">+", undef >> no longer leaks memory when TMPDIR is set
3562but points to a directory a temporary file cannot be created in. [perl
3563#120951]
3564
3565=item *
3566
3567C< for ( $h{k} || '' ) > no longer auto-vivifies C<$h{k}>. [perl
3568#120374]
3569
3570=item *
3571
3572On Windows machines, Perl now emulates the POSIX use of the environment
3573for locale initialization. Previously, the environment was ignored.
3574See L<perllocale/ENVIRONMENT>.
3575
3576=item *
3577
3578Fixed a crash when destroying a self-referencing GLOB. [perl #121242]
3579
3580=back
3581
3582=head1 Known Problems
3583
3584=over 4
3585
3586=item *
3587
3588L<IO::Socket> is known to fail tests on AIX 5.3. There is
3589L<a patch|https://rt.perl.org/Ticket/Display.html?id=120835> in the request
3590tracker, #120835, which may be applied to future releases.
3591
3592=item *
3593
3594The following modules are known to have test failures with this version of
3595Perl. Patches have been submitted, so there will hopefully be new releases
3596soon:
3597
3598=over
3599
3600=item *
3601
3602L<Data::Structure::Util> version 0.15
3603
3604=item *
3605
3606L<HTML::StripScripts> version 1.05
3607
3608=item *
3609
3610L<List::Gather> version 0.08.
3611
3612=back
3613
3614=back
3615
3616=head1 Obituary
3617
3618Diana Rosa, 27, of Rio de Janeiro, went to her long rest on May 10,
36192014, along with the plush camel she kept hanging on her computer screen
3620all the time. She was a passionate Perl hacker who loved the language and its
3621community, and who never missed a Rio.pm event. She was a true artist, an
3622enthusiast about writing code, singing arias and graffiting walls. We'll never
3623forget you.
3624
3625Greg McCarroll died on August 28, 2013.
3626
3627Greg was well known for many good reasons. He was one of the organisers of
3628the first YAPC::Europe, which concluded with an unscheduled auction where he
3629frantically tried to raise extra money to avoid the conference making a
3630loss. It was Greg who mistakenly arrived for a london.pm meeting a week
3631late; some years later he was the one who sold the choice of official
3632meeting date at a YAPC::Europe auction, and eventually as glorious leader of
3633london.pm he got to inherit the irreverent confusion that he had created.
3634
3635Always helpful, friendly and cheerfully optimistic, you will be missed, but
3636never forgotten.
3637
3638=head1 Acknowledgements
3639
3640Perl 5.20.0 represents approximately 12 months of development since Perl 5.18.0
3641and contains approximately 470,000 lines of changes across 2,900 files from 124
3642authors.
3643
3644Excluding auto-generated files, documentation and release tools, there were
3645approximately 280,000 lines of changes to 1,800 .pm, .t, .c and .h files.
3646
3647Perl continues to flourish into its third decade thanks to a vibrant community
3648of users and developers. The following people are known to have contributed the
3649improvements that became Perl 5.20.0:
3650
3651Aaron Crane, Abhijit Menon-Sen, Abigail, Abir Viqar, Alan Haggai Alavi, Alan
3652Hourihane, Alexander Voronov, Alexandr Ciornii, Andy Dougherty, Anno Siegel,
3653Aristotle Pagaltzis, Arthur Axel 'fREW' Schmidt, Brad Gilbert, Brendan Byrd,
3654Brian Childs, Brian Fraser, Brian Gottreu, Chris 'BinGOs' Williams, Christian
3655Millour, Colin Kuskie, Craig A. Berry, Dabrien 'Dabe' Murphy, Dagfinn Ilmari
3656Mannsåker, Daniel Dragan, Darin McBride, David Golden, David Leadbeater, David
3657Mitchell, David Nicol, David Steinbrunner, Dennis Kaarsemaker, Dominic
3658Hargreaves, Ed Avis, Eric Brine, Evan Zacks, Father Chrysostomos, Florian
3659Ragwitz, François Perrad, Gavin Shelley, Gideon Israel Dsouza, Gisle Aas,
3660Graham Knop, H.Merijn Brand, Hauke D, Heiko Eissfeldt, Hiroo Hayashi, Hojung
3661Youn, James E Keenan, Jarkko Hietaniemi, Jerry D. Hedden, Jess Robinson, Jesse
3662Luehrs, Johan Vromans, John Gardiner Myers, John Goodyear, John P. Linderman,
3663John Peacock, kafka, Kang-min Liu, Karen Etheridge, Karl Williamson, Keedi Kim,
3664Kent Fredric, kevin dawson, Kevin Falcone, Kevin Ryde, Leon Timmermans, Lukas
3665Mai, Marc Simpson, Marcel Grünauer, Marco Peereboom, Marcus Holland-Moritz,
3666Mark Jason Dominus, Martin McGrath, Matthew Horsfall, Max Maischein, Mike
3667Doherty, Moritz Lenz, Nathan Glenn, Nathan Trapuzzano, Neil Bowers, Neil
3668Williams, Nicholas Clark, Niels Thykier, Niko Tyni, Olivier Mengué, Owain G.
3669Ainsworth, Paul Green, Paul Johnson, Peter John Acklam, Peter Martini, Peter
3670Rabbitson, Petr Písař, Philip Boulain, Philip Guenther, Piotr Roszatycki,
3671Rafael Garcia-Suarez, Reini Urban, Reuben Thomas, Ricardo Signes, Ruslan
3672Zakirov, Sergey Alekseev, Shirakata Kentaro, Shlomi Fish, Slaven Rezic,
3673Smylers, Steffen Müller, Steve Hay, Sullivan Beck, Thomas Sibley, Tobias
3674Leich, Toby Inkster, Tokuhiro Matsuno, Tom Christiansen, Tom Hukins, Tony Cook,
3675Victor Efimov, Viktor Turskyi, Vladimir Timofeev, YAMASHINA Hio, Yves Orton,
3676Zefram, Zsbán Ambrus, Ævar Arnfjörð Bjarmason.
3677
3678The list above is almost certainly incomplete as it is automatically generated
3679from version control history. In particular, it does not include the names of
3680the (very much appreciated) contributors who reported issues to the Perl bug
3681tracker.
3682
3683Many of the changes included in this version originated in the CPAN modules
3684included in Perl's core. We're grateful to the entire CPAN community for
3685helping Perl to flourish.
3686
3687For a more complete list of all of Perl's historical contributors, please see
3688the F<AUTHORS> file in the Perl source distribution.
3689
3690=head1 Reporting Bugs
3691
3692If you find what you think is a bug, you might check the articles recently
3693posted to the comp.lang.perl.misc newsgroup and the perl bug database at
3694http://rt.perl.org/perlbug/ . There may also be information at
3695http://www.perl.org/ , the Perl Home Page.
3696
3697If you believe you have an unreported bug, please run the L<perlbug> program
3698included with your release. Be sure to trim your bug down to a tiny but
3699sufficient test case. Your bug report, along with the output of C<perl -V>,
3700will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
3701
3702If the bug you are reporting has security implications, which make it
3703inappropriate to send to a publicly archived mailing list, then please send it
3704to perl5-security-report@perl.org. This points to a closed subscription
3705unarchived mailing list, which includes all the core committers, who will be
3706able to help assess the impact of issues, figure out a resolution, and help
3707co-ordinate the release of patches to mitigate or fix the problem across all
3708platforms on which Perl is supported. Please only use this address for
3709security issues in the Perl core, not for modules independently distributed on
3710CPAN.
3711
3712=head1 SEE ALSO
3713
3714The F<Changes> file for an explanation of how to view exhaustive details on
3715what changed.
3716
3717The F<INSTALL> file for how to build Perl.
3718
3719The F<README> file for general stuff.
3720
3721The F<Artistic> and F<Copying> files for copyright information.
3722
3723=cut