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perl5299delta: Clarify variable-length lookbehind entry
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1=encoding utf8
2
3=head1 NAME
4
5perl5299delta - what is new for perl v5.29.9
6
7=head1 DESCRIPTION
8
9This document describes differences between the 5.29.8 release and the 5.29.9
10release.
11
12If you are upgrading from an earlier release such as 5.29.7, first read
13L<perl5298delta>, which describes differences between 5.29.7 and 5.29.8.
14
15=head1 Core Enhancements
16
17=head2 Wildcards in Unicode property value specifications are now
18partially supported
19
20You can now do something like this in a regular expression pattern
21
22 qr! \p{nv= /(?x) \A [0-5] \z / }!
23
24which matches all Unicode code points which have numeric value is
25between 0 and 5 inclusive.
26
27This marks another step in implementing the regular expression features
28the Unicode Consortium suggests.
29
30Most properties are supported, with the remainder planned for 5.32.
31Details are in L<perlunicode/Wildcards in Property Values>.
32
33=head2 qr'\N{name}' is now supported
34
35Previously it was an error to evaluate a named character C<\N{...}>
36within a single quoted regular expression pattern (whose evaluation is
37deferred from the normal place). This restriction is now removed.
38
39=head2 Unicode 12.0 is supported
40
41For details, see L<https://www.unicode.org/versions/Unicode12.0.0/>.
42
43Because of a change in Unicode release cycles, Perl jumps from Unicode
4410.0 in Perl 5.28 to Unicode 12.0 in Perl 5.30.
45
46=head2 It is now possible to compile perl to always use thread-safe
47locale operations.
48
49Previously, these calls were only used when the perl was compiled to be
50multi-threaded. To always enable them, add
51
52 -Accflags='-DUSE_THREAD_SAFE_LOCALE'
53
54to your F<Configure> flags.
55
56
57=head1 Security
58
59=head2 Variable length lookbehind in regular expression pattern matching
60is now experimentally supported
61
f6f85064 62Using a lookbehind assertion (like C<(?<=foo?)> or C<(?<!ba{1,9}r)> previously
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63would generate an error and refuse to compile. Now it compiles (if the
64maximum lookbehind is at most 255 characters), but raises a warning in
65the new C<experimental::vlb> warnings category. This is to caution you
66that the precise behavior is subject to change based on feedback from
67use in the field.
68
69See L<perlre/(?<=pattern)> and L<perlre/(?<!pattern)>.
70
71=head1 Incompatible Changes
72
73=head2 C<pack()> no longer can return malformed UTF-8
74
75It croaks if it would otherwise return a UTF-8 string that contains
76malformed UTF-8. This protects agains potential security threats. This
77is considered a bug fix as well ([perl #131642]).
78
79=head2 Any set of digits in the Common script are legal in a script run
80of another script
81
82There are several sets of digits in the Common script. C<[0-9]> is the
83most familiar. But there are also C<[\x{FF10}-\x{FF19}]> (FULLWIDTH
84DIGIT ZERO - FULLWIDTH DIGIT NINE), and several sets for use in
85mathematical notation, such as the MATHEMATICAL DOUBLE-STRUCK DIGITs.
86Any of these sets should be able to appear in script runs of, say,
87Greek. But the design of 5.30 overlooked all but the ASCII digits
88C<[0-9]>, so the design was flawed. This has been fixed, so is both a
89bug fix and an incompatibility. [perl #133547]
90
91All digits in a run still have to come from the same set of ten digits.
92
93=head1 Modules and Pragmata
94
95=head2 Updated Modules and Pragmata
96
97=over 4
98
99=item *
100
101L<Devel::PPPort> has been upgraded from version 3.44 to 3.45.
102
103=item *
104
105L<Encode> has been upgraded from version 3.00 to 3.01.
106
107=item *
108
109L<ExtUtils::Manifest> has been upgraded from version 1.71 to 1.72.
110
111=item *
112
113L<JSON::PP> has been upgraded from version 4.00 to 4.02.
114
115=item *
116
117L<Module::CoreList> has been upgraded from version 5.20190220 to 5.20190320.
118
119=item *
120
121L<perl5db.pl> has been upgraded from version 1.54 to 1.55.
122
123Debugging threaded code no longer deadlocks in C<DB::sub> nor
124C<DB::lsub>.
125
126=item *
127
128L<PerlIO::encoding> has been upgraded from version 0.26 to 0.27.
129
130Warnings enabled by setting the C<WARN_ON_ERR> flag in
131C<$PerlIO::encoding::fallback> are now only produced if warnings are
132enabled with C<use warnings "utf8";> or setting C<$^W>.
133
134=item *
135
136L<threads::shared> has been upgraded from version 1.59 to 1.60.
137
138Added support for extra tracing of locking, this requires a
139C<-DDEBUGGING> and extra compilation flags.
140
141=item *
142
143L<utf8> has been upgraded from version 1.21 to 1.22.
144
145=item *
146
147L<warnings> has been upgraded from version 1.43 to 1.44.
148
149=back
150
151=head1 Diagnostics
152
153The following additions or changes have been made to diagnostic output,
154including warnings and fatal error messages. For the complete list of
155diagnostic messages, see L<perldiag>.
156
157=head2 Changes to Existing Diagnostics
158
159=over 4
160
161=item *
162
163Specifying C<\o{}> without anything between the braces now yields the
164fatal error message "Empty \o{}". Previously it was "Number with no
165digits". This means the same wording is used for this kind of error as
166with similar constructs such as C<\p{}>.
167
168=item *
169
170Within the scope of the experimental feature C<use re 'strict'>,
171specifying C<\x{}> without anything between the braces now yields the
172fatal error message "Empty \x{}". Previously it was "Number with no
173digits". This means the same wording is used for this kind of error as
174with similar constructs such as C<\p{}>. It is legal, though not wise
175to have an empty C<\x> outside of C<re 'strict'>; it silently generates
176a NUL character.
177
178=back
179
180=head1 Internal Changes
181
182=over 4
183
184=item *
185
186Added C<newSVsv_nomg()> to copy a SV without processing get magic on
187the source. [perl #132964]
188
189=back
190
191=head1 Selected Bug Fixes
192
193=over 4
194
195=item *
196
197C<pack()> no longer can return malformed UTF-8. It croaks if it would
198otherwise return a UTF-8 string that contains malformed UTF-8. This
199protects agains potential security threats. [perl #131642]
200
201=item *
202
203See L</Any set of digits in the Common script are legal in a script run
204of another script>.
205
206=back
207
208=head1 Acknowledgements
209
210Perl 5.29.9 represents approximately 4 weeks of development since Perl
2115.29.8 and contains approximately 47,000 lines of changes across 210 files
212from 11 authors.
213
214Excluding auto-generated files, documentation and release tools, there were
215approximately 38,000 lines of changes to 71 .pm, .t, .c and .h files.
216
217Perl continues to flourish into its fourth decade thanks to a vibrant
218community of users and developers. The following people are known to have
219contributed the improvements that became Perl 5.29.9:
220
221Chris 'BinGOs' Williams, Craig A. Berry, Dagfinn Ilmari Mannsåker, Dan
222Kogai, David Mitchell, Karen Etheridge, Karl Williamson, Nicolas R., Pali,
223Tony Cook, Unicode Consortium.
224
225The list above is almost certainly incomplete as it is automatically
226generated from version control history. In particular, it does not include
227the names of the (very much appreciated) contributors who reported issues to
228the Perl bug tracker.
229
230Many of the changes included in this version originated in the CPAN modules
231included in Perl's core. We're grateful to the entire CPAN community for
232helping Perl to flourish.
233
234For a more complete list of all of Perl's historical contributors, please
235see the F<AUTHORS> file in the Perl source distribution.
236
237=head1 Reporting Bugs
238
239If you find what you think is a bug, you might check the perl bug database
240at L<https://rt.perl.org/>. There may also be information at
241L<http://www.perl.org/>, the Perl Home Page.
242
243If you believe you have an unreported bug, please run the L<perlbug> program
244included with your release. Be sure to trim your bug down to a tiny but
245sufficient test case. Your bug report, along with the output of C<perl -V>,
246will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
247
248If the bug you are reporting has security implications which make it
249inappropriate to send to a publicly archived mailing list, then see
250L<perlsec/SECURITY VULNERABILITY CONTACT INFORMATION>
251for details of how to report the issue.
252
253=head1 Give Thanks
254
255If you wish to thank the Perl 5 Porters for the work we had done in Perl 5,
256you can do so by running the C<perlthanks> program:
257
258 perlthanks
259
260This will send an email to the Perl 5 Porters list with your show of thanks.
261
262=head1 SEE ALSO
263
264The F<Changes> file for an explanation of how to view exhaustive details on
265what changed.
266
267The F<INSTALL> file for how to build Perl.
268
269The F<README> file for general stuff.
270
271The F<Artistic> and F<Copying> files for copyright information.
272
273=cut