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perldelta: note a few interesting changes
[perl5.git] / pod / perldelta.pod
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1=encoding utf8
2
3=head1 NAME
4
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5[ this is a template for a new perldelta file. Any text flagged as
6XXX needs to be processed before release. ]
27f00e3d 7
e96e0834 8perldelta - what is new for perl v5.17.2
417a992d 9
e96e0834 10=head1 DESCRIPTION
028c8719 11
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12This document describes differences between the 5.17.1 release and
13the 5.17.2 release.
028c8719 14
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15If you are upgrading from an earlier release such as 5.17.0, first read
16L<perl5171delta>, which describes differences between 5.17.0 and
175.17.1.
028c8719 18
e96e0834 19=head1 Notice
30608892 20
e96e0834 21XXX Any important notices here
e128ab2c 22
e96e0834 23=head1 Core Enhancements
e128ab2c 24
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25XXX New core language features go here. Summarise user-visible core language
26enhancements. Particularly prominent performance optimisations could go
27here, but most should go in the L</Performance Enhancements> section.
fe3193b5 28
e96e0834 29[ List each enhancement as a =head2 entry ]
05c8f9ed 30
e96e0834 31=head1 Security
0da72d5e 32
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33XXX Any security-related notices go here. In particular, any security
34vulnerabilities closed should be noted here rather than in the
35L</Selected Bug Fixes> section.
0da72d5e 36
e96e0834 37[ List each security issue as a =head2 entry ]
0da72d5e 38
e96e0834 39=head1 Incompatible Changes
0da72d5e 40
e96e0834 41XXX For a release on a stable branch, this section aspires to be:
0da72d5e 42
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43 There are no changes intentionally incompatible with 5.XXX.XXX
44 If any exist, they are bugs, and we request that you submit a
45 report. See L</Reporting Bugs> below.
0da72d5e 46
e96e0834 47[ List each incompatible change as a =head2 entry ]
e2f0c3bb 48
e96e0834 49=head1 Deprecations
e2f0c3bb 50
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51XXX Any deprecated features, syntax, modules etc. should be listed here.
52In particular, deprecated modules should be listed here even if they are
53listed as an updated module in the L</Modules and Pragmata> section.
7d101ed1 54
e96e0834 55[ List each deprecation as a =head2 entry ]
7d101ed1 56
e96e0834 57=head1 Performance Enhancements
7d101ed1 58
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59XXX Changes which enhance performance without changing behaviour go here. There
60may well be none in a stable release.
7d101ed1 61
e96e0834 62[ List each enhancement as a =item entry ]
95ce428c 63
f9001595 64=over 4
75ff5956 65
2630d42b 66=item *
c11980ad 67
e96e0834 68XXX
53de3ff0 69
61174fb5 70=back
ef7131e9 71
61174fb5 72=head1 Modules and Pragmata
ef7131e9 73
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74XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
75go here. If Module::CoreList is updated, generate an initial draft of the
76following sections using F<Porting/corelist-perldelta.pl>, which prints stub
77entries to STDOUT. Results can be pasted in place of the '=head2' entries
78below. A paragraph summary for important changes should then be added by hand.
79In an ideal world, dual-life modules would have a F<Changes> file that could be
80cribbed.
5cefbec9 81
e96e0834 82[ Within each section, list entries as a =item entry ]
fbdb83f3 83
e96e0834 84=head2 New Modules and Pragmata
95c6c5c5 85
e96e0834 86=over 4
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87
88=item *
89
e96e0834 90XXX
95c6c5c5 91
e96e0834 92=back
ff3f295c 93
e96e0834 94=head2 Updated Modules and Pragmata
ff3f295c 95
e96e0834 96=over 4
95c6c5c5 97
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98=item *
99
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100L<File::stat> has been upgraded from version 1.06 to 1.07.
101
102Previously C<File::stat>'s overloaded C<-x> and C<-X> operators did not give
103the correct results for directories or executable files when running as
104root. They had been treating executable permissions for root just like for
105any other user, performing group membership tests I<etc> for files not owned
106by root. They now follow the correct Unix behaviour - for a directory they
107are always true, and for a file if any of the three execute permission bits
108are set then they report that root can execute the file. Perl's builtin
109C<-x> and C<-X> operators have always been correct.
c506fc7e 110
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111=item *
112
113L<Tie::StdHandle> has been upgraded from version 4.2 to 4.3.
114
115C<READ> now respects the offset argument to C<read> [perl #112826].
116
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117=item *
118
119L<IO> has been upgraded from version 1.25_07 to 1.25_08.
120
121L<IO::Socket> tries harder to cache or otherwise fetch socket
122information.
123
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124=item *
125
126L<Storable> has been upgraded from version 2.36 to 2.37.
127
128Restricted hashes were not always thawed correctly [perl #73972].
129
130Storable would croak when freezing a blessed REF object with a
131C<STORABLE_freeze()> method [perl #113880].
132
e96e0834 133=back
c506fc7e 134
e96e0834 135=head2 Removed Modules and Pragmata
c506fc7e 136
e96e0834 137=over 4
95c6c5c5 138
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139=item *
140
e96e0834 141XXX
95c6c5c5 142
e96e0834 143=back
95c6c5c5 144
e96e0834 145=head1 Documentation
95c6c5c5 146
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147XXX Changes to files in F<pod/> go here. Consider grouping entries by
148file and be sure to link to the appropriate page, e.g. L<perlfunc>.
95c6c5c5 149
e96e0834 150=head2 New Documentation
1c633914 151
e96e0834 152XXX Changes which create B<new> files in F<pod/> go here.
f558db2f 153
e96e0834 154=head3 L<XXX>
66aa79e2 155
e96e0834 156XXX Description of the purpose of the new file here
95c6c5c5 157
e96e0834 158=head2 Changes to Existing Documentation
95c6c5c5 159
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160XXX Changes which significantly change existing files in F<pod/> go here.
161However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
162section.
95c6c5c5 163
66b30015 164=head3 L<perlfunc>
95c6c5c5 165
e96e0834 166=over 4
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167
168=item *
169
66b30015 170Clarified documentation of C<our>.
95c6c5c5 171
e96e0834 172=back
95c6c5c5 173
e96e0834 174=head1 Diagnostics
95c6c5c5 175
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176The following additions or changes have been made to diagnostic output,
177including warnings and fatal error messages. For the complete list of
178diagnostic messages, see L<perldiag>.
95c6c5c5 179
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180XXX New or changed warnings emitted by the core's C<C> code go here. Also
181include any changes in L<perldiag> that reconcile it to the C<C> code.
71014848 182
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183[ Within each section, list entries as a =item entry that links to perldiag,
184 e.g.
71014848 185
e96e0834 186 =item *
95c6c5c5 187
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188 L<Invalid version object|perldiag/"Invalid version object">
189]
95c6c5c5 190
e96e0834 191=head2 New Diagnostics
95c6c5c5 192
e96e0834 193XXX Newly added diagnostic messages go here
95c6c5c5 194
e96e0834 195=head3 New Errors
95c6c5c5 196
e96e0834 197=over 4
95c6c5c5 198
95c6c5c5
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199=item *
200
a9be10f4 201L<Group name must start with a non-digit word character in regex; marked by <-- HERE in mE<sol>%sE<sol>|perldiag/"Group name must start with a non-digit word character in regex; marked by <-- HERE in m/%s/">
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202
203This error has been added for C<(?&0)>, which is invalid. It used to
204produce an incomprehensible error message [perl #101666].
95c6c5c5 205
e96e0834 206=back
95c6c5c5 207
e96e0834 208=head3 New Warnings
95c6c5c5 209
e96e0834 210=over 4
95c6c5c5 211
95c6c5c5
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212=item *
213
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214C<chr()> now warns when passed a negative value [perl #83048].
215
216=item *
217
218C<srand()> now warns when passed a value that doesn't fit in a C<UV> (since the
219value will be truncated rather than overflowing) [perl #40605].
7d101ed1 220
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221=item *
222
223Running perl with the C<-i> flag now warns if no input files are provided on
224the command line [perl #113410].
225
e96e0834 226=back
d9661073 227
e96e0834 228=head2 Changes to Existing Diagnostics
95c6c5c5 229
e96e0834 230XXX Changes (i.e. rewording) of diagnostic messages go here
95c6c5c5 231
e96e0834 232=over 4
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233
234=item *
235
e96e0834 236XXX Describe change here
3630f57e 237
e96e0834 238=back
3630f57e 239
e96e0834 240=head1 Utility Changes
95c6c5c5 241
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242XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go
243here. Most of these are built within the directories F<utils> and F<x2p>.
95c6c5c5 244
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245[ List utility changes as a =head3 entry for each utility and =item
246entries for each change
247Use L<XXX> with program names to get proper documentation linking. ]
95c6c5c5 248
e96e0834 249=head3 L<XXX>
95c6c5c5 250
e96e0834 251=over 4
95c6c5c5
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252
253=item *
254
e96e0834 255XXX
95c6c5c5 256
e96e0834 257=back
95c6c5c5 258
e96e0834 259=head1 Configuration and Compilation
95c6c5c5 260
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261XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
262go here. Any other changes to the Perl build process should be listed here.
263However, any platform-specific changes should be listed in the
264L</Platform Support> section, instead.
95c6c5c5 265
e96e0834 266[ List changes as a =item entry ].
95c6c5c5 267
e96e0834 268=over 4
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269
270=item *
271
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272Building perl with some Windows compilers used to fail due to a problem
273with miniperl's C<glob> operator (which uses the C<perlglob> program)
274deleting the PATH environment variable [perl #113798].
95c6c5c5 275
e96e0834 276=back
95c6c5c5 277
e96e0834 278=head1 Testing
95c6c5c5 279
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280XXX Any significant changes to the testing of a freshly built perl should be
281listed here. Changes which create B<new> files in F<t/> go here as do any
282large changes to the testing harness (e.g. when parallel testing was added).
283Changes to existing files in F<t/> aren't worth summarising, although the bugs
284that they represent may be covered elsewhere.
95c6c5c5 285
e96e0834 286[ List each test improvement as a =item entry ]
95c6c5c5 287
e96e0834 288=over 4
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289
290=item *
291
e96e0834 292XXX
95c6c5c5 293
61174fb5 294=back
f558db2f 295
e96e0834 296=head1 Platform Support
05c8f9ed 297
e96e0834 298XXX Any changes to platform support should be listed in the sections below.
05c8f9ed 299
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300[ Within the sections, list each platform as a =item entry with specific
301changes as paragraphs below it. ]
9dea6244 302
e96e0834 303=head2 New Platforms
9dea6244 304
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305XXX List any platforms that this version of perl compiles on, that previous
306versions did not. These will either be enabled by new files in the F<hints/>
307directories, or new subdirectories and F<README> files at the top level of the
308source tree.
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309
310=over 4
311
b81e0e29 312=item *
7d101ed1 313
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314Configure now always adds -qlanglvl=extc99 to the CC flags on AIX when
315using xlC. This will make it easier to compile a number of XS-based modules
316that assume C99 [perl #113778].
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317
318=back
319
e96e0834 320=head2 Discontinued Platforms
ef7131e9 321
e96e0834 322XXX List any platforms that this version of perl no longer compiles on.
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323
324=over 4
325
e96e0834 326=item XXX-some-platform
8dffc0ab 327
e96e0834 328XXX
dbc84d79 329
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330=back
331
61174fb5 332=head2 Platform-Specific Notes
ceb0881c 333
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334XXX List any changes for specific platforms. This could include configuration
335and compilation changes or changes in portability/compatibility. However,
336changes within modules for platforms should generally be listed in the
337L</Modules and Pragmata> section.
89cbc6b8 338
e96e0834 339=over 4
0998713f 340
5edb02d0 341=item VMS
112b6866 342
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343Quotes are now removed from the command verb (but not the parameters) for commands
344spawned via C<system>, backticks, or a piped C<open>. Previously, quotes on the verb
345were passed through to DCL, which would fail to recognize the command. Also, if the
346verb is actually a path to an image or command procedure on an ODS-5 volume, quoting it
347now allows the path to contain spaces.
112b6866 348
61174fb5 349=back
8e125188 350
61174fb5 351=head1 Internal Changes
8e125188 352
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353XXX Changes which affect the interface available to C<XS> code go here.
354Other significant internal changes for future core maintainers should
355be noted as well.
c4643160 356
e96e0834 357[ List each change as a =item entry ]
f8ef51fd 358
e96e0834 359=over 4
e128ab2c 360
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361=item *
362
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363OP allocation for CVs now uses a slab allocator. This simplifies
364memory management for OPs allocated to a CV, so cleaning up after a
365compilation error is simpler and safer [perl #111462][perl #112312].
e2f0c3bb 366
61174fb5 367=back
422287bf 368
61174fb5 369=head1 Selected Bug Fixes
2de6ba8d 370
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371XXX Important bug fixes in the core language are summarised here.
372Bug fixes in files in F<ext/> and F<lib/> are best summarised in
373L</Modules and Pragmata>.
52c4b146 374
e96e0834 375[ List each fix as a =item entry ]
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376
377=over 4
378
379=item *
380
48895a0d 381A regression introduced in v5.14.0 has been fixed, in which some calls
7ab2ea42 382to the C<re> module would clobber C<$_> [perl #113750].
e128ab2c 383
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384=item *
385
386C<do FILE> now always either sets or clears C<$@>, even when the file can't be
387read. This ensures that testing C<$@> first (as recommended by the
388documentation) always returns the correct result.
389
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390=item *
391
392The array iterator used for the C<each @array> construct is now correctly
393reset when C<@array> is cleared (RT #75596). This happens for example when the
394array is globally assigned to, as in C<@array = (...)>, but not when its
395B<values> are assigned to. In terms of the XS API, it means that C<av_clear()>
396will now reset the iterator.
397
398This mirrors the behaviour of the hash iterator when the hash is cleared.
399
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400=item *
401
402C<< $class->can >>, C<< $class->isa >>, and C<< $class->DOES >> now return
403correct results, regardless of whether that package referred to by C<$class>
404exists [perl #47113].
405
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406=item *
407
408Arriving signals no longer clear C<$@> [perl #45173].
409
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410=item *
411
412Allow C<my ()> declarations with an empty variable list [perl #113554].
413
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414=item *
415
416During parsing, subs declared after errors no longer leave stubs
417[perl #113712].
418
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419=item *
420
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421Closures containing no string evals no longer hang on to their containing
422subroutines, allowing variables closed over by outer subroutines to be
423freed when the outer sub is freed, even if the inner sub still exists
424[perl #89544].
425
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426=item *
427
428Duplication of in-memory filehandles by opening with a "<&=" or ">&=" mode
429stopped working properly in 5.16.0. It was causing the new handle to
430reference a different scalar variable. This has been fixed [perl #113764].
431
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432=item *
433
434C<qr//> expressions no longer crash with custom regular expression engines
435that do not set C<offs> at regular expression compilation time
436[perl #112962].
437
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438=item *
439
440C<delete local> no longer crashes with certain magical arrays and hashes
441[perl #112966].
442
443=item *
444
445C<local> on elements of certain magical arrays and hashes used not to
446arrange to have the element deleted on scope exit, even if the element did
447not exist before C<local>.
448
449=item *
450
451C<scalar(write)> no longer returns multiple items [perl #73690].
452
453=item *
454
455String to floating point conversions no longer misparse certain strings under
456C<use locale> [perl #109318].
457
458=item *
459
460C<@INC> filters that die no longer leak memory [perl #92252].
461
462=item *
463
464The implementations of overloaded operations are now called in the correct
465context. This allows, among other things, being able to properly override
466C<< <> >> [perl #47119].
467
468=item *
469
470Specifying only the C<fallback> key when calling C<use overload> now behaves
471properly [perl #113010].
472
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473=item *
474
475C<< sub foo { my $a = 0; while ($a) { ... } } >> and
476C<< sub foo { while (0) { ... } } >> now return the same thing [perl #73618].
477
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478=item *
479
480Fixed the debugger C<l> and C<M> commends, and other debugger
481functionality which was broken in 5.17.0 [perl #113918].
482
483=item *
484
485String negation now behaves the same under C<use integer;> as it does
486without [perl #113012].
487
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488=back
489
e96e0834 490=head1 Known Problems
dbc84d79 491
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492XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
493tests that had to be C<TODO>ed for the release would be noted here. Unfixed
494platform specific bugs also go here.
53de3ff0 495
e96e0834 496[ List each fix as a =item entry ]
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497
498=over 4
499
500=item *
501
e96e0834 502XXX
233bba44 503
e96e0834 504=back
233bba44 505
e96e0834 506=head1 Obituary
233bba44 507
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508XXX If any significant core contributor has died, we've added a short obituary
509here.
233bba44 510
61174fb5 511=head1 Acknowledgements
d5dc7001 512
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513XXX Generate this with:
514
515 perl Porting/acknowledgements.pl v5.17.1..HEAD
29cf780c 516
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517=head1 Reporting Bugs
518
519If you find what you think is a bug, you might check the articles
52deee2e 520recently posted to the comp.lang.perl.misc newsgroup and the perl
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521bug database at http://rt.perl.org/perlbug/ . There may also be
522information at http://www.perl.org/ , the Perl Home Page.
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523
524If you believe you have an unreported bug, please run the L<perlbug>
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525program included with your release. Be sure to trim your bug down
526to a tiny but sufficient test case. Your bug report, along with the
527output of C<perl -V>, will be sent off to perlbug@perl.org to be
528analysed by the Perl porting team.
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529
530If the bug you are reporting has security implications, which make it
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531inappropriate to send to a publicly archived mailing list, then please send
532it to perl5-security-report@perl.org. This points to a closed subscription
533unarchived mailing list, which includes
534all the core committers, who will be able
535to help assess the impact of issues, figure out a resolution, and help
536co-ordinate the release of patches to mitigate or fix the problem across all
537platforms on which Perl is supported. Please only use this address for
538security issues in the Perl core, not for modules independently
539distributed on CPAN.
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540
541=head1 SEE ALSO
542
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543The F<Changes> file for an explanation of how to view exhaustive details
544on what changed.
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545
546The F<INSTALL> file for how to build Perl.
547
548The F<README> file for general stuff.
549
550The F<Artistic> and F<Copying> files for copyright information.
551
552=cut