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<Encode> has been upgraded from version 2.60_01 to 2.62.
179 B<piconv> now has better error handling when the encoding name is nonexistent,
180 and a build breakage when upgrading L<Encode> in perl-5.8.2 and earlier has
185 The libnet collection of modules has been upgraded from version 1.25 to 1.27.
187 There are only whitespace changes to the installed files.
191 L<Math::BigInt> has been upgraded from version 1.9993 to 1.9994.
193 Synchronize POD changes from the CPAN release.
195 C<< Math::BigFloat->blog(x) >> would sometimes return blog(2*x) when
196 the accuracy was greater than 70 digits.
198 The result of C<< Math::BigFloat->bdiv() >> in list context now
199 satisfies C<< x = quotient * divisor + remainder >>.
203 L<Math::BigRat> has been upgraded from version 0.2606 to 0.2607.
205 Synchronize POD changes from the CPAN release.
209 L<perl5db.pl> has been upgraded from version 1.44 to 1.45.
211 fork() in the debugger under C<tmux> will now create a new window for
212 the forked process. L<[perl
213 #121333]|https://rt.perl.org/Ticket/Display.html?id=121333>
215 The debugger now saves the current working directory on startup and
216 restores it when you restart your program with C<R> or <rerun>. L<[perl
217 #121509]|https://rt.perl.org/Ticket/Display.html?id=121509>
219 L<Unicode::Collate> has been upgraded from version 1.04 to 1.07.
221 Version 0.67's improved discontiguous contractions is invalidated by default
222 and is supported as a parameter 'long_contraction'.
226 L<Unicode::Normalize> has been upgraded from version 1.17 to 1.18.
228 The XSUB implementation has been removed in favour of pure Perl.
232 =head2 Removed Modules and Pragmata
244 XXX Changes to files in F<pod/> go here. Consider grouping entries by
245 file and be sure to link to the appropriate page, e.g. L<perlfunc>.
247 =head2 New Documentation
249 XXX Changes which create B<new> files in F<pod/> go here.
253 XXX Description of the purpose of the new file here
255 =head2 Changes to Existing Documentation
257 XXX Changes which significantly change existing files in F<pod/> go here.
258 However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
267 XXX Description of the change here
273 The following additions or changes have been made to diagnostic output,
274 including warnings and fatal error messages. For the complete list of
275 diagnostic messages, see L<perldiag>.
277 XXX New or changed warnings emitted by the core's C<C> code go here. Also
278 include any changes in L<perldiag> that reconcile it to the C<C> code.
280 =head2 New Diagnostics
282 XXX Newly added diagnostic messages go under here, separated into New Errors
291 XXX L<message|perldiag/"message">
301 XXX L<message|perldiag/"message">
305 =head2 Changes to Existing Diagnostics
307 XXX Changes (i.e. rewording) of diagnostic messages go here
313 L<Unsuccessful %s on filename containing newline|perldiag/"Unsuccessful %s on filename containing newline">
315 This warning is now only produced when the newline is at the end of
320 =head1 Utility Changes
322 XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go here.
323 Most of these are built within the directories F<utils> and F<x2p>.
325 [ List utility changes as a =head2 entry for each utility and =item
326 entries for each change
327 Use L<XXX> with program names to get proper documentation linking. ]
339 =head1 Configuration and Compilation
341 XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
342 go here. Any other changes to the Perl build process should be listed here.
343 However, any platform-specific changes should be listed in the
344 L</Platform Support> section, instead.
346 [ List changes as a =item entry ].
358 XXX Any significant changes to the testing of a freshly built perl should be
359 listed here. Changes which create B<new> files in F<t/> go here as do any
360 large changes to the testing harness (e.g. when parallel testing was added).
361 Changes to existing files in F<t/> aren't worth summarizing, although the bugs
362 that they represent may be covered elsewhere.
364 [ List each test improvement as a =item entry ]
374 =head1 Platform Support
376 XXX Any changes to platform support should be listed in the sections below.
378 [ Within the sections, list each platform as a =item entry with specific
379 changes as paragraphs below it. ]
383 XXX List any platforms that this version of perl compiles on, that previous
384 versions did not. These will either be enabled by new files in the F<hints/>
385 directories, or new subdirectories and F<README> files at the top level of the
390 =item XXX-some-platform
396 =head2 Discontinued Platforms
398 XXX List any platforms that this version of perl no longer compiles on.
402 =item XXX-some-platform
408 =head2 Platform-Specific Notes
410 XXX List any changes for specific platforms. This could include configuration
411 and compilation changes or changes in portability/compatibility. However,
412 changes within modules for platforms should generally be listed in the
413 L</Modules and Pragmata> section.
417 =item XXX-some-platform
423 =head1 Internal Changes
425 XXX Changes which affect the interface available to C<XS> code go here. Other
426 significant internal changes for future core maintainers should be noted as
433 The deprecated variable C<PL_sv_objcount> has been removed.
437 =head1 Selected Bug Fixes
439 XXX Important bug fixes in the core language are summarized here. Bug fixes in
440 files in F<ext/> and F<lib/> are best summarized in L</Modules and Pragmata>.
442 [ List each fix as a =item entry ]
448 index() and rindex() no longer crash when used on strings over 2GB in
450 L<[perl #121562]|https://rt.perl.org/Ticket/Display.html?id=121562>.
454 =head1 Known Problems
456 XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
457 tests that had to be C<TODO>ed for the release would be noted here. Unfixed
458 platform specific bugs also go here.
460 [ List each fix as a =item entry ]
470 =head1 Errata From Previous Releases
476 XXX Add anything here that we forgot to add, or were mistaken about, in
477 the perldelta of a previous release.
483 XXX If any significant core contributor has died, we've added a short obituary
486 =head1 Acknowledgements
488 XXX Generate this with:
490 perl Porting/acknowledgements.pl v5.21.1..HEAD
492 =head1 Reporting Bugs
494 If you find what you think is a bug, you might check the articles recently
495 posted to the comp.lang.perl.misc newsgroup and the perl bug database at
496 https://rt.perl.org/ . There may also be information at
497 http://www.perl.org/ , the Perl Home Page.
499 If you believe you have an unreported bug, please run the L<perlbug> program
500 included with your release. Be sure to trim your bug down to a tiny but
501 sufficient test case. Your bug report, along with the output of C<perl -V>,
502 will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
504 If the bug you are reporting has security implications, which make it
505 inappropriate to send to a publicly archived mailing list, then please send it
506 to perl5-security-report@perl.org. This points to a closed subscription
507 unarchived mailing list, which includes all the core committers, who will be
508 able to help assess the impact of issues, figure out a resolution, and help
509 co-ordinate the release of patches to mitigate or fix the problem across all
510 platforms on which Perl is supported. Please only use this address for
511 security issues in the Perl core, not for modules independently distributed on
516 The F<Changes> file for an explanation of how to view exhaustive details on
519 The F<INSTALL> file for how to build Perl.
521 The F<README> file for general stuff.
523 The F<Artistic> and F<Copying> files for copyright information.