5 [ this is a template for a new perldelta file. Any text flagged as XXX needs
6 to be processed before release. ]
8 perldelta - what is new for perl v5.21.1
12 This document describes differences between the 5.21.0 release and the 5.21.1
15 If you are upgrading from an earlier release such as 5.20.0, first read
16 L<perl5210delta>, which describes differences between 5.20.0 and 5.21.0.
20 XXX Any important notices here
22 =head1 Core Enhancements
24 XXX New core language features go here. Summarize user-visible core language
25 enhancements. Particularly prominent performance optimisations could go
26 here, but most should go in the L</Performance Enhancements> section.
28 [ List each enhancement as a =head2 entry ]
30 =head2 C<qr/foo/x> now ignores any Unicode pattern white space
32 The C</x> regular expression modifier allows the pattern to contain
33 white space and comments, both of which are ignored, for improved
34 readability. Until now, not all the white space characters that Unicode
35 designates for this purpose were handled. The additional ones now
38 U+200E LEFT-TO-RIGHT MARK,
39 U+200F RIGHT-TO-LEFT MARK,
40 U+2028 LINE SEPARATOR,
42 U+2029 PARAGRAPH SEPARATOR.
44 =head2 S<C<use locale>> can restrict which locale categories are affected
46 It is now possible to pass a parameter to S<C<use locale>> to specify
47 a subset of locale categories to be locale-aware, with the remaining
48 ones unaffected. See L<perllocale/The "use locale" pragma> for details.
52 XXX Any security-related notices go here. In particular, any security
53 vulnerabilities closed should be noted here rather than in the
54 L</Selected Bug Fixes> section.
56 [ List each security issue as a =head2 entry ]
58 =head1 Incompatible Changes
60 XXX For a release on a stable branch, this section aspires to be:
62 There are no changes intentionally incompatible with 5.XXX.XXX
63 If any exist, they are bugs, and we request that you submit a
64 report. See L</Reporting Bugs> below.
66 =head2 In double-quotish C<\cI<X>>, I<X> must now be a printable ASCII character
68 In prior releases, failure to do this raised a deprecation warning.
70 =head2 Splitting the tokens C<(?> and C<(*> in regular expressions is
71 now a fatal compilation error.
73 These had been deprecated since v5.18.
75 =head2 5 additional characters are treated as white space under C</x> in
76 regex patterns (unless escaped)
78 The use of these characters with C</x> outside bracketed character
79 classes and when not preceeded by a backslash has raised a deprecation
80 warning since v5.18. Now they will be ignored. See L</qrE<sol>fooE<sol>x>
81 for the list of the five characters.
83 =head2 Comment lines within S<C<(?[ ])>> now are ended only by a C<\n>
85 S<C<(?[ ])>> is an experimental feature, introduced in v5.18. It operates
86 as if C</x> is always enabled. But there was a difference, comment
87 lines (following a C<#> character) were terminated by anything matching
88 C<\R> which includes all vertical whitespace, such as form feeds. For
89 consistency, this is now changed to match what terminates comment lines
90 outside S<C<(?[ ])>>, namely a C<\n> (even if escaped), which is the
91 same as what terminates a heredoc string and formats.
93 =head2 Omitting % and @ on hash and array names is no longer permitted
95 Really old Perl let you omit the @ on array names and the % on hash
96 names in some spots. This has issued a deprecation warning since Perl
97 5.0, and is no longer permitted.
101 XXX Any deprecated features, syntax, modules etc. should be listed here.
103 =head2 Using a NO-BREAK space in a character alias for C<\N{...}> is now
106 This non-graphic character is essentially indistinguishable from a
107 regular space, and so should not be allowed. See
108 L<charnames/CUSTOM ALIASES>.
110 =head2 Module removals
112 XXX Remove this section if inapplicable.
114 The following modules will be removed from the core distribution in a
115 future release, and will at that time need to be installed from CPAN.
116 Distributions on CPAN which require these modules will need to list them as
119 The core versions of these modules will now issue C<"deprecated">-category
120 warnings to alert you to this fact. To silence these deprecation warnings,
121 install the modules in question from CPAN.
123 Note that these are (with rare exceptions) fine modules that you are encouraged
124 to continue to use. Their disinclusion from core primarily hinges on their
125 necessity to bootstrapping a fully functional, CPAN-capable Perl installation,
126 not usually on concerns over their design.
132 XXX Note that deprecated modules should be listed here even if they are listed
133 as an updated module in the L</Modules and Pragmata> section.
137 [ List each other deprecation as a =head2 entry ]
139 =head1 Performance Enhancements
141 XXX Changes which enhance performance without changing behaviour go here.
142 There may well be none in a stable release.
144 [ List each enhancement as a =item entry ]
154 =head1 Modules and Pragmata
156 XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
157 go here. If Module::CoreList is updated, generate an initial draft of the
158 following sections using F<Porting/corelist-perldelta.pl>. A paragraph summary
159 for important changes should then be added by hand. In an ideal world,
160 dual-life modules would have a F<Changes> file that could be cribbed.
162 [ Within each section, list entries as a =item entry ]
164 =head2 New Modules and Pragmata
174 =head2 Updated Modules and Pragmata
180 L<Carp> has been upgraded from version 1.3301 to 1.34.
182 Carp::Heavy now ignores version mismatches with Carp if Carp is newer
183 than 1.12, since Carp::Heavy's guts were merged into Carp at that
185 L<[perl #121574]|https://rt.perl.org/Ticket/Display.html?id=121574>
189 L<Encode> has been upgraded from version 2.60_01 to 2.62.
191 B<piconv> now has better error handling when the encoding name is nonexistent,
192 and a build breakage when upgrading L<Encode> in perl-5.8.2 and earlier has
197 The libnet collection of modules has been upgraded from version 1.25 to 1.27.
199 There are only whitespace changes to the installed files.
203 The Locale-Codes collection of modules has been upgraded from vesion 3.30 to 3.31.
205 Fixed a bug in the scripts used to extract data from spreadsheets that
206 prevented the SHP currency code from being found.
207 L<[cpan #94229]|https://rt.cpan.org/Ticket/Display.html?id=94229>
211 L<Math::BigInt> has been upgraded from version 1.9993 to 1.9994.
213 Synchronize POD changes from the CPAN release.
215 C<< Math::BigFloat->blog(x) >> would sometimes return blog(2*x) when
216 the accuracy was greater than 70 digits.
218 The result of C<< Math::BigFloat->bdiv() >> in list context now
219 satisfies C<< x = quotient * divisor + remainder >>.
223 L<Math::BigRat> has been upgraded from version 0.2606 to 0.2607.
225 Synchronize POD changes from the CPAN release.
229 L<Module::Metadata> has been upgraded from version 1.000022 to 1.000024.
231 Support installations on older perls with an L<ExtUtils::MakeMaker> earlier
236 L<perl5db.pl> has been upgraded from version 1.44 to 1.45.
240 A mismatch between the documentation and the code in utf8::downgrade()
241 was fixed in favour of the documentation. The optional second argument
242 is now correctly treated as a perl boolean (true/false semantics) and
247 fork() in the debugger under C<tmux> will now create a new window for
248 the forked process. L<[perl
249 #121333]|https://rt.perl.org/Ticket/Display.html?id=121333>
251 The debugger now saves the current working directory on startup and
252 restores it when you restart your program with C<R> or <rerun>. L<[perl
253 #121509]|https://rt.perl.org/Ticket/Display.html?id=121509>
255 L<Unicode::Collate> has been upgraded from version 1.04 to 1.07.
257 Version 0.67's improved discontiguous contractions is invalidated by default
258 and is supported as a parameter 'long_contraction'.
262 L<Unicode::Normalize> has been upgraded from version 1.17 to 1.18.
264 The XSUB implementation has been removed in favour of pure Perl.
268 L<Hash::Util> has been upgraded from version 0.16 to 0.17.
270 Minor bug fixes and documentation fixes to Hash::Util::hash_stats()
275 =head2 Removed Modules and Pragmata
287 XXX Changes to files in F<pod/> go here. Consider grouping entries by
288 file and be sure to link to the appropriate page, e.g. L<perlfunc>.
290 =head2 New Documentation
292 XXX Changes which create B<new> files in F<pod/> go here.
296 XXX Description of the purpose of the new file here
298 =head2 Changes to Existing Documentation
300 XXX Changes which significantly change existing files in F<pod/> go here.
301 However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
310 XXX Description of the change here
316 The following additions or changes have been made to diagnostic output,
317 including warnings and fatal error messages. For the complete list of
318 diagnostic messages, see L<perldiag>.
320 XXX New or changed warnings emitted by the core's C<C> code go here. Also
321 include any changes in L<perldiag> that reconcile it to the C<C> code.
323 =head2 New Diagnostics
325 XXX Newly added diagnostic messages go under here, separated into New Errors
334 XXX L<message|perldiag/"message">
344 XXX L<message|perldiag/"message">
348 =head2 Changes to Existing Diagnostics
350 XXX Changes (i.e. rewording) of diagnostic messages go here
356 L<Unsuccessful %s on filename containing newline|perldiag/"Unsuccessful %s on filename containing newline">
358 This warning is now only produced when the newline is at the end of
363 =head1 Utility Changes
365 XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go here.
366 Most of these are built within the directories F<utils> and F<x2p>.
368 [ List utility changes as a =head2 entry for each utility and =item
369 entries for each change
370 Use L<XXX> with program names to get proper documentation linking. ]
382 =head1 Configuration and Compilation
384 XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
385 go here. Any other changes to the Perl build process should be listed here.
386 However, any platform-specific changes should be listed in the
387 L</Platform Support> section, instead.
389 [ List changes as a =item entry ].
401 XXX Any significant changes to the testing of a freshly built perl should be
402 listed here. Changes which create B<new> files in F<t/> go here as do any
403 large changes to the testing harness (e.g. when parallel testing was added).
404 Changes to existing files in F<t/> aren't worth summarizing, although the bugs
405 that they represent may be covered elsewhere.
407 [ List each test improvement as a =item entry ]
417 =head1 Platform Support
419 XXX Any changes to platform support should be listed in the sections below.
421 [ Within the sections, list each platform as a =item entry with specific
422 changes as paragraphs below it. ]
426 XXX List any platforms that this version of perl compiles on, that previous
427 versions did not. These will either be enabled by new files in the F<hints/>
428 directories, or new subdirectories and F<README> files at the top level of the
433 =item XXX-some-platform
439 =head2 Discontinued Platforms
441 XXX List any platforms that this version of perl no longer compiles on.
445 =item XXX-some-platform
451 =head2 Platform-Specific Notes
453 XXX List any changes for specific platforms. This could include configuration
454 and compilation changes or changes in portability/compatibility. However,
455 changes within modules for platforms should generally be listed in the
456 L</Modules and Pragmata> section.
460 =item XXX-some-platform
466 =head1 Internal Changes
468 XXX Changes which affect the interface available to C<XS> code go here. Other
469 significant internal changes for future core maintainers should be noted as
476 The deprecated variable C<PL_sv_objcount> has been removed.
480 Perl now tries to keep the locale category C<LC_NUMERIC> set to "C"
481 except around operations that need it to be set to the program's
482 underlying locale. This protects the many XS modules that cannot cope
483 with the decimal radix character not being a dot. Prior to this
484 release, Perl initialized this category to "C", but a call to
485 C<POSIX::setlocale()> would change it. Now such a call will change the
486 underlying locale of the C<LC_NUMERIC> category for the program, but the
487 locale exposed to XS code will remain "C". There is an API under
488 development for those relatively few modules that need to use the
489 underlying locale. This API will be nailed down during the course of
490 developing v5.21. Send email to L<mailto:perl5-porters@perl.org> for
495 =head1 Selected Bug Fixes
497 XXX Important bug fixes in the core language are summarized here. Bug fixes in
498 files in F<ext/> and F<lib/> are best summarized in L</Modules and Pragmata>.
500 [ List each fix as a =item entry ]
506 index() and rindex() no longer crash when used on strings over 2GB in
508 L<[perl #121562]|https://rt.perl.org/Ticket/Display.html?id=121562>.
512 A small previously intentional memory leak in PERL_SYS_INIT/PERL_SYS_INIT3 on
513 Win32 builds was fixed. This might affect embedders who repeatedly create and
514 destroy perl engines within the same process.
518 C<POSIX::localeconv()> now returns the data for the program's underlying
519 locale even when called from outside the scope of S<C<use locale>>.
523 C<POSIX::localeconv()> now works properly on platforms which don't have
524 C<LC_NUMERIC> and/or C<LC_MONETARY>, or for which Perl has been compiled
525 to disregard either or both of these locale categories. In such
526 circumstances, there are now no entries for the corresponding values in
527 the hash returned by C<localeconv()>.
531 C<POSIX::localeconv()> now marks appropriately the values it returns as
532 UTF-8 or not. Previously they were always returned as a bytes, even if
533 they were supposed to be encoded as UTF-8.
537 =head1 Known Problems
539 XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
540 tests that had to be C<TODO>ed for the release would be noted here. Unfixed
541 platform specific bugs also go here.
543 [ List each fix as a =item entry ]
553 =head1 Errata From Previous Releases
559 XXX Add anything here that we forgot to add, or were mistaken about, in
560 the perldelta of a previous release.
566 XXX If any significant core contributor has died, we've added a short obituary
569 =head1 Acknowledgements
571 XXX Generate this with:
573 perl Porting/acknowledgements.pl v5.21.1..HEAD
575 =head1 Reporting Bugs
577 If you find what you think is a bug, you might check the articles recently
578 posted to the comp.lang.perl.misc newsgroup and the perl bug database at
579 https://rt.perl.org/ . There may also be information at
580 http://www.perl.org/ , the Perl Home Page.
582 If you believe you have an unreported bug, please run the L<perlbug> program
583 included with your release. Be sure to trim your bug down to a tiny but
584 sufficient test case. Your bug report, along with the output of C<perl -V>,
585 will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
587 If the bug you are reporting has security implications, which make it
588 inappropriate to send to a publicly archived mailing list, then please send it
589 to perl5-security-report@perl.org. This points to a closed subscription
590 unarchived mailing list, which includes all the core committers, who will be
591 able to help assess the impact of issues, figure out a resolution, and help
592 co-ordinate the release of patches to mitigate or fix the problem across all
593 platforms on which Perl is supported. Please only use this address for
594 security issues in the Perl core, not for modules independently distributed on
599 The F<Changes> file for an explanation of how to view exhaustive details on
602 The F<INSTALL> file for how to build Perl.
604 The F<README> file for general stuff.
606 The F<Artistic> and F<Copying> files for copyright information.