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.
46 XXX Any security-related notices go here. In particular, any security
47 vulnerabilities closed should be noted here rather than in the
48 L</Selected Bug Fixes> section.
50 [ List each security issue as a =head2 entry ]
52 =head1 Incompatible Changes
54 XXX For a release on a stable branch, this section aspires to be:
56 There are no changes intentionally incompatible with 5.XXX.XXX
57 If any exist, they are bugs, and we request that you submit a
58 report. See L</Reporting Bugs> below.
60 =head2 In double-quotish C<\cI<X>>, I<X> must now be a printable ASCII character
62 In prior releases, failure to do this raised a deprecation warning.
64 =head2 Splitting the tokens C<(?> and C<(*> in regular expressions is
65 now a fatal compilation error.
67 These had been deprecated since v5.18.
69 =head2 5 additional characters are treated as white space under C</x> in
70 regex patterns (unless escaped)
72 The use of these characters with C</x> outside bracketed character
73 classes and when not preceeded by a backslash has raised a deprecation
74 warning since v5.18. Now they will be ignored. See L</qrE<sol>fooE<sol>x>
75 for the list of the five characters.
77 =head2 Comment lines within S<C<(?[ ])>> now are ended only by a C<\n>
79 S<C<(?[ ])>> is an experimental feature, introduced in v5.18. It operates
80 as if C</x> is always enabled. But there was a difference, comment
81 lines (following a C<#> character) were terminated by anything matching
82 C<\R> which includes all vertical whitespace, such as form feeds. For
83 consistency, this is now changed to match what terminates comment lines
84 outside S<C<(?[ ])>>, namely a C<\n> (even if escaped), which is the
85 same as what terminates a heredoc string and formats.
89 XXX Any deprecated features, syntax, modules etc. should be listed here.
91 =head2 Using a NO-BREAK space in a character alias for C<\N{...}> is now
94 This non-graphic character is essentially indistinguishable from a
95 regular space, and so should not be allowed. See
96 L<charnames/CUSTOM ALIASES>.
98 =head2 Module removals
100 XXX Remove this section if inapplicable.
102 The following modules will be removed from the core distribution in a
103 future release, and will at that time need to be installed from CPAN.
104 Distributions on CPAN which require these modules will need to list them as
107 The core versions of these modules will now issue C<"deprecated">-category
108 warnings to alert you to this fact. To silence these deprecation warnings,
109 install the modules in question from CPAN.
111 Note that these are (with rare exceptions) fine modules that you are encouraged
112 to continue to use. Their disinclusion from core primarily hinges on their
113 necessity to bootstrapping a fully functional, CPAN-capable Perl installation,
114 not usually on concerns over their design.
120 XXX Note that deprecated modules should be listed here even if they are listed
121 as an updated module in the L</Modules and Pragmata> section.
125 [ List each other deprecation as a =head2 entry ]
127 =head1 Performance Enhancements
129 XXX Changes which enhance performance without changing behaviour go here.
130 There may well be none in a stable release.
132 [ List each enhancement as a =item entry ]
142 =head1 Modules and Pragmata
144 XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
145 go here. If Module::CoreList is updated, generate an initial draft of the
146 following sections using F<Porting/corelist-perldelta.pl>. A paragraph summary
147 for important changes should then be added by hand. In an ideal world,
148 dual-life modules would have a F<Changes> file that could be cribbed.
150 [ Within each section, list entries as a =item entry ]
152 =head2 New Modules and Pragmata
162 =head2 Updated Modules and Pragmata
168 L<Carp> has been upgraded from version 1.3301 to 1.34.
170 Carp::Heavy now ignores version mismatches with Carp if Carp is newer
171 than 1.12, since Carp::Heavy's guts were merged into Carp at that
173 L<[perl #121574]|https://rt.perl.org/Ticket/Display.html?id=121574>
177 L<Math::BigInt> has been upgraded from version 1.9993 to 1.9994.
179 Synchronize POD changes from the CPAN release.
181 C<< Math::BigFloat->blog(x) >> would sometimes return blog(2*x) when
182 the accuracy was greater than 70 digits.
184 The result of C<< Math::BigFloat->bdiv() >> in list context now
185 satisfies C<< x = quotient * divisor + remainder >>.
189 L<Math::BigRat> has been upgraded from version 0.2606 to 0.2607.
191 Synchronize POD changes from the CPAN release.
195 L<perl5db.pl> has been upgraded from version 1.44 to 1.45.
197 fork() in the debugger under C<tmux> will now create a new window for
198 the forked process. L<[perl
199 #121333]|https://rt.perl.org/Ticket/Display.html?id=121333>
201 The debugger now saves the current working directory on startup and
202 restores it when you restart your program with C<R> or <rerun>. L<[perl
203 #121509]|https://rt.perl.org/Ticket/Display.html?id=121509>
205 L<Unicode::Collate> has been upgraded from version 1.04 to 1.07.
207 Version 0.67's improved discontiguous contractions is invalidated by default
208 and is supported as a parameter 'long_contraction'.
212 L<Unicode::Normalize> has been upgraded from version 1.17 to 1.18.
214 The XSUB implementation has been removed in favour of pure Perl.
218 =head2 Removed Modules and Pragmata
230 XXX Changes to files in F<pod/> go here. Consider grouping entries by
231 file and be sure to link to the appropriate page, e.g. L<perlfunc>.
233 =head2 New Documentation
235 XXX Changes which create B<new> files in F<pod/> go here.
239 XXX Description of the purpose of the new file here
241 =head2 Changes to Existing Documentation
243 XXX Changes which significantly change existing files in F<pod/> go here.
244 However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
253 XXX Description of the change here
259 The following additions or changes have been made to diagnostic output,
260 including warnings and fatal error messages. For the complete list of
261 diagnostic messages, see L<perldiag>.
263 XXX New or changed warnings emitted by the core's C<C> code go here. Also
264 include any changes in L<perldiag> that reconcile it to the C<C> code.
266 =head2 New Diagnostics
268 XXX Newly added diagnostic messages go under here, separated into New Errors
277 XXX L<message|perldiag/"message">
287 XXX L<message|perldiag/"message">
291 =head2 Changes to Existing Diagnostics
293 XXX Changes (i.e. rewording) of diagnostic messages go here
299 L<Unsuccessful %s on filename containing newline|perldiag/"Unsuccessful %s on filename containing newline">
301 This warning is now only produced when the newline is at the end of
306 =head1 Utility Changes
308 XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go here.
309 Most of these are built within the directories F<utils> and F<x2p>.
311 [ List utility changes as a =head2 entry for each utility and =item
312 entries for each change
313 Use L<XXX> with program names to get proper documentation linking. ]
325 =head1 Configuration and Compilation
327 XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
328 go here. Any other changes to the Perl build process should be listed here.
329 However, any platform-specific changes should be listed in the
330 L</Platform Support> section, instead.
332 [ List changes as a =item entry ].
344 XXX Any significant changes to the testing of a freshly built perl should be
345 listed here. Changes which create B<new> files in F<t/> go here as do any
346 large changes to the testing harness (e.g. when parallel testing was added).
347 Changes to existing files in F<t/> aren't worth summarizing, although the bugs
348 that they represent may be covered elsewhere.
350 [ List each test improvement as a =item entry ]
360 =head1 Platform Support
362 XXX Any changes to platform support should be listed in the sections below.
364 [ Within the sections, list each platform as a =item entry with specific
365 changes as paragraphs below it. ]
369 XXX List any platforms that this version of perl compiles on, that previous
370 versions did not. These will either be enabled by new files in the F<hints/>
371 directories, or new subdirectories and F<README> files at the top level of the
376 =item XXX-some-platform
382 =head2 Discontinued Platforms
384 XXX List any platforms that this version of perl no longer compiles on.
388 =item XXX-some-platform
394 =head2 Platform-Specific Notes
396 XXX List any changes for specific platforms. This could include configuration
397 and compilation changes or changes in portability/compatibility. However,
398 changes within modules for platforms should generally be listed in the
399 L</Modules and Pragmata> section.
403 =item XXX-some-platform
409 =head1 Internal Changes
411 XXX Changes which affect the interface available to C<XS> code go here. Other
412 significant internal changes for future core maintainers should be noted as
419 The deprecated variable C<PL_sv_objcount> has been removed.
423 =head1 Selected Bug Fixes
425 XXX Important bug fixes in the core language are summarized here. Bug fixes in
426 files in F<ext/> and F<lib/> are best summarized in L</Modules and Pragmata>.
428 [ List each fix as a =item entry ]
434 index() and rindex() no longer crash when used on strings over 2GB in
436 L<[perl #121562]|https://rt.perl.org/Ticket/Display.html?id=121562>.
440 =head1 Known Problems
442 XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
443 tests that had to be C<TODO>ed for the release would be noted here. Unfixed
444 platform specific bugs also go here.
446 [ List each fix as a =item entry ]
456 =head1 Errata From Previous Releases
462 XXX Add anything here that we forgot to add, or were mistaken about, in
463 the perldelta of a previous release.
469 XXX If any significant core contributor has died, we've added a short obituary
472 =head1 Acknowledgements
474 XXX Generate this with:
476 perl Porting/acknowledgements.pl v5.21.1..HEAD
478 =head1 Reporting Bugs
480 If you find what you think is a bug, you might check the articles recently
481 posted to the comp.lang.perl.misc newsgroup and the perl bug database at
482 https://rt.perl.org/ . There may also be information at
483 http://www.perl.org/ , the Perl Home Page.
485 If you believe you have an unreported bug, please run the L<perlbug> program
486 included with your release. Be sure to trim your bug down to a tiny but
487 sufficient test case. Your bug report, along with the output of C<perl -V>,
488 will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
490 If the bug you are reporting has security implications, which make it
491 inappropriate to send to a publicly archived mailing list, then please send it
492 to perl5-security-report@perl.org. This points to a closed subscription
493 unarchived mailing list, which includes all the core committers, who will be
494 able to help assess the impact of issues, figure out a resolution, and help
495 co-ordinate the release of patches to mitigate or fix the problem across all
496 platforms on which Perl is supported. Please only use this address for
497 security issues in the Perl core, not for modules independently distributed on
502 The F<Changes> file for an explanation of how to view exhaustive details on
505 The F<INSTALL> file for how to build Perl.
507 The F<README> file for general stuff.
509 The F<Artistic> and F<Copying> files for copyright information.