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1=encoding utf8
2
3=head1 NAME
4
5ed58cbd 5perldelta - what is new for perl v5.18.0
e128ab2c 6
4eabcf70 7=head1 DESCRIPTION
6db9054f 8
e612b5a0 9This document describes differences between the v5.16.0 release and the v5.18.0
e08634c5 10release.
6db9054f 11
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12If you are upgrading from an earlier release such as v5.14.0, first read
13L<perl5160delta>, which describes differences between v5.14.0 and v5.16.0.
3f01b192 14
5ed58cbd 15=head1 Core Enhancements
3f01b192 16
5ed58cbd 17=head2 New mechanism for experimental features
82d98f72 18
5ed58cbd 19Newly-added experimental features will now require this incantation:
82d98f72 20
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21 no warnings "experimental::feature_name";
22 use feature "feature_name"; # would warn without the prev line
23
24There is a new warnings category, called "experimental", containing
25warnings that the L<feature> pragma emits when enabling experimental
26features.
27
28Newly-added experimental features will also be given special warning IDs,
29which consist of "experimental::" followed by the name of the feature. (The
30plan is to extend this mechanism eventually to all warnings, to allow them
31to be enabled or disabled individually, and not just by category.)
32
33By saying
34
35 no warnings "experimental::feature_name";
36
37you are taking responsibility for any breakage that future changes to, or
38removal of, the feature may cause.
39
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40Since some features (like C<~~> or C<my $_>) now emit experimental warnings,
41and you may want to disable them in code that is also run on perls that do not
42recognize these warning categories, consider using the C<if> pragma like this:
43
5c46a73f 44 no if $] >= 5.018, 'warnings', "experimental::feature_name";
1ea0ff56 45
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46Existing experimental features may begin emitting these warnings, too. Please
47consult L<perlexperiment> for information on which features are considered
48experimental.
49
50=head2 Hash overhaul
51
e612b5a0 52Changes to the implementation of hashes in perl v5.18.0 will be one of the most
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53visible changes to the behavior of existing code.
54
8e74b2ed 55By default, two distinct hash variables with identical keys and values may now
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56provide their contents in a different order where it was previously identical.
57
58When encountering these changes, the key to cleaning up from them is to accept
59that B<hashes are unordered collections> and to act accordingly.
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60
61=head3 Hash randomization
62
63The seed used by Perl's hash function is now random. This means that the
64order which keys/values will be returned from functions like C<keys()>,
65C<values()>, and C<each()> will differ from run to run.
66
67This change was introduced to make Perl's hashes more robust to algorithmic
68complexity attacks, and also because we discovered that it exposes hash
69ordering dependency bugs and makes them easier to track down.
70
71Toolchain maintainers might want to invest in additional infrastructure to
72test for things like this. Running tests several times in a row and then
73comparing results will make it easier to spot hash order dependencies in
74code. Authors are strongly encouraged not to expose the key order of
75Perl's hashes to insecure audiences.
76
77Further, every hash has its own iteration order, which should make it much
78more difficult to determine what the current hash seed is.
79
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80=head3 New hash functions
81
e612b5a0 82Perl v5.18 includes support for multiple hash functions, and changed
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83the default (to ONE_AT_A_TIME_HARD), you can choose a different
84algorithm by defining a symbol at compile time. For a current list,
e612b5a0 85consult the F<INSTALL> document. Note that as of Perl v5.18 we can
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86only recommend use of the default or SIPHASH. All the others are
87known to have security issues and are for research purposes only.
5ed58cbd 88
f105b7be 89=head3 PERL_HASH_SEED environment variable now takes a hex value
5ed58cbd 90
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91C<PERL_HASH_SEED> no longer accepts an integer as a parameter;
92instead the value is expected to be a binary value encoded in a hex
93string, such as "0xf5867c55039dc724". This is to make the
94infrastructure support hash seeds of arbitrary lengths, which might
ad94908e 95exceed that of an integer. (SipHash uses a 16 byte seed.)
5ed58cbd 96
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97=head3 PERL_PERTURB_KEYS environment variable added
98
f105b7be 99The C<PERL_PERTURB_KEYS> environment variable allows one to control the level of
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100randomization applied to C<keys> and friends.
101
f105b7be 102When C<PERL_PERTURB_KEYS> is 0, perl will not randomize the key order at all. The
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103chance that C<keys> changes due to an insert will be the same as in previous
104perls, basically only when the bucket size is changed.
105
f105b7be 106When C<PERL_PERTURB_KEYS> is 1, perl will randomize keys in a non-repeatable
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107way. The chance that C<keys> changes due to an insert will be very high. This
108is the most secure and default mode.
109
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110When C<PERL_PERTURB_KEYS> is 2, perl will randomize keys in a repeatable way.
111Repeated runs of the same program should produce the same output every time.
c40c48bb 112
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113C<PERL_HASH_SEED> implies a non-default C<PERL_PERTURB_KEYS> setting. Setting
114C<PERL_HASH_SEED=0> (exactly one 0) implies C<PERL_PERTURB_KEYS=0> (hash key
115randomization disabled); settng C<PERL_HASH_SEED> to any other value implies
116C<PERL_PERTURB_KEYS=2> (deterministic and repeatable hash key randomization).
117Specifying C<PERL_PERTURB_KEYS> explicitly to a different level overrides this
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118behavior.
119
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120=head3 Hash::Util::hash_seed() now returns a string
121
122Hash::Util::hash_seed() now returns a string instead of an integer. This
123is to make the infrastructure support hash seeds of arbitrary lengths
ad94908e 124which might exceed that of an integer. (SipHash uses a 16 byte seed.)
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125
126=head3 Output of PERL_HASH_SEED_DEBUG has been changed
127
128The environment variable PERL_HASH_SEED_DEBUG now makes perl show both the
f105b7be 129hash function perl was built with, I<and> the seed, in hex, in use for that
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130process. Code parsing this output, should it exist, must change to accommodate
131the new format. Example of the new format:
132
133 $ PERL_HASH_SEED_DEBUG=1 ./perl -e1
134 HASH_FUNCTION = MURMUR3 HASH_SEED = 0x1476bb9f
135
136=head2 Upgrade to Unicode 6.2
137
2e7bc647 138Perl now supports Unicode 6.2. A list of changes from Unicode
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1396.1 is at L<http://www.unicode.org/versions/Unicode6.2.0>.
140
141=head2 Character name aliases may now include non-Latin1-range characters
142
143It is possible to define your own names for characters for use in
144C<\N{...}>, C<charnames::vianame()>, etc. These names can now be
145comprised of characters from the whole Unicode range. This allows for
146names to be in your native language, and not just English. Certain
147restrictions apply to the characters that may be used (you can't define
148a name that has punctuation in it, for example). See L<charnames/CUSTOM
149ALIASES>.
150
151=head2 New DTrace probes
152
153The following new DTrace probes have been added:
14731ad1 154
337fb649 155=over 4
14731ad1 156
82d98f72 157=item *
14731ad1 158
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159C<op-entry>
160
161=item *
162
163C<loading-file>
164
165=item *
166
167C<loaded-file>
168
169=back
170
171=head2 C<${^LAST_FH}>
172
173This new variable provides access to the filehandle that was last read.
174This is the handle used by C<$.> and by C<tell> and C<eof> without
175arguments.
176
177=head2 Regular Expression Set Operations
178
179This is an B<experimental> feature to allow matching against the union,
180intersection, etc., of sets of code points, similar to
181L<Unicode::Regex::Set>. It can also be used to extend C</x> processing
182to [bracketed] character classes, and as a replacement of user-defined
183properties, allowing more complex expressions than they do. See
184L<perlrecharclass/Extended Bracketed Character Classes>.
185
186=head2 Lexical subroutines
187
188This new feature is still considered B<experimental>. To enable it:
189
190 use 5.018;
191 no warnings "experimental::lexical_subs";
192 use feature "lexical_subs";
193
194You can now declare subroutines with C<state sub foo>, C<my sub foo>, and
195C<our sub foo>. (C<state sub> requires that the "state" feature be
196enabled, unless you write it as C<CORE::state sub foo>.)
197
198C<state sub> creates a subroutine visible within the lexical scope in which
199it is declared. The subroutine is shared between calls to the outer sub.
200
201C<my sub> declares a lexical subroutine that is created each time the
202enclosing block is entered. C<state sub> is generally slightly faster than
203C<my sub>.
204
205C<our sub> declares a lexical alias to the package subroutine of the same
206name.
207
208For more information, see L<perlsub/Lexical Subroutines>.
209
210=head2 Computed Labels
211
212The loop controls C<next>, C<last> and C<redo>, and the special C<dump>
213operator, now allow arbitrary expressions to be used to compute labels at run
214time. Previously, any argument that was not a constant was treated as the
215empty string.
216
217=head2 More CORE:: subs
218
219Several more built-in functions have been added as subroutines to the
220CORE:: namespace - namely, those non-overridable keywords that can be
221implemented without custom parsers: C<defined>, C<delete>, C<exists>,
222C<glob>, C<pos>, C<protoytpe>, C<scalar>, C<split>, C<study>, and C<undef>.
223
224As some of these have prototypes, C<prototype('CORE::...')> has been
225changed to not make a distinction between overridable and non-overridable
226keywords. This is to make C<prototype('CORE::pos')> consistent with
227C<prototype(&CORE::pos)>.
228
229=head2 C<kill> with negative signal names
230
231C<kill> has always allowed a negative signal number, which kills the
232process group instead of a single process. It has also allowed signal
233names. But it did not behave consistently, because negative signal names
234were treated as 0. Now negative signals names like C<-INT> are supported
235and treated the same way as -2 [perl #112990].
236
237=head1 Security
238
239=head2 C<Storable> security warning in documentation
240
241The documentation for C<Storable> now includes a section which warns readers
242of the danger of accepting Storable documents from untrusted sources. The
243short version is that deserializing certain types of data can lead to loading
244modules and other code execution. This is documented behavior and wanted
245behavior, but this opens an attack vector for malicious entities.
246
247=head2 C<Locale::Maketext> allowed code injection via a malicious template
248
249If users could provide a translation string to Locale::Maketext, this could be
250used to invoke arbitrary Perl subroutines available in the current process.
251
252This has been fixed, but it is still possible to invoke any method provided by
253C<Locale::Maketext> itself or a subclass that you are using. One of these
254methods in turn will invoke the Perl core's C<sprintf> subroutine.
255
256In summary, allowing users to provide translation strings without auditing
257them is a bad idea.
258
259This vulnerability is documented in CVE-2012-6329.
260
261=head2 Avoid calling memset with a negative count
262
263Poorly written perl code that allows an attacker to specify the count to perl's
264C<x> string repeat operator can already cause a memory exhaustion
e612b5a0 265denial-of-service attack. A flaw in versions of perl before v5.15.5 can escalate
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266that into a heap buffer overrun; coupled with versions of glibc before 2.16, it
267possibly allows the execution of arbitrary code.
268
269The flaw addressed to this commit has been assigned identifier CVE-2012-5195
270and was researched by Tim Brown.
271
272=head1 Incompatible Changes
273
274=head2 See also: hash overhaul
275
276Some of the changes in the L<hash overhaul|/"Hash overhaul"> are not fully
277compatible with previous versions of perl. Please read that section.
278
279=head2 An unknown character name in C<\N{...}> is now a syntax error
280
281Previously, it warned, and the Unicode REPLACEMENT CHARACTER was
282substituted. Unicode now recommends that this situation be a syntax
283error. Also, the previous behavior led to some confusing warnings and
284behaviors, and since the REPLACEMENT CHARACTER has no use other than as
285a stand-in for some unknown character, any code that has this problem is
286buggy.
287
288=head2 Formerly deprecated characters in C<\N{}> character name aliases are now errors.
289
290Since v5.12.0, it has been deprecated to use certain characters in
291user-defined C<\N{...}> character names. These now cause a syntax
292error. For example, it is now an error to begin a name with a digit,
293such as in
294
295 my $undraftable = "\N{4F}"; # Syntax error!
296
237b9c6d 297or to have commas anywhere in the name. See L<charnames/CUSTOM ALIASES>.
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298
299=head2 C<\N{BELL}> now refers to U+1F514 instead of U+0007
300
301Unicode 6.0 reused the name "BELL" for a different code point than it
302traditionally had meant. Since Perl v5.14, use of this name still
303referred to U+0007, but would raise a deprecation warning. Now, "BELL"
304refers to U+1F514, and the name for U+0007 is "ALERT". All the
305functions in L<charnames> have been correspondingly updated.
306
307=head2 New Restrictions in Multi-Character Case-Insensitive Matching in Regular Expression Bracketed Character Classes
308
309Unicode has now withdrawn their previous recommendation for regular
310expressions to automatically handle cases where a single character can
237b9c6d 311match multiple characters case-insensitively, for example, the letter
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312LATIN SMALL LETTER SHARP S and the sequence C<ss>. This is because
313it turns out to be impracticable to do this correctly in all
314circumstances. Because Perl has tried to do this as best it can, it
315will continue to do so. (We are considering an option to turn it off.)
316However, a new restriction is being added on such matches when they
317occur in [bracketed] character classes. People were specifying
318things such as C</[\0-\xff]/i>, and being surprised that it matches the
319two character sequence C<ss> (since LATIN SMALL LETTER SHARP S occurs in
320this range). This behavior is also inconsistent with using a
321property instead of a range: C<\p{Block=Latin1}> also includes LATIN
322SMALL LETTER SHARP S, but C</[\p{Block=Latin1}]/i> does not match C<ss>.
323The new rule is that for there to be a multi-character case-insensitive
324match within a bracketed character class, the character must be
325explicitly listed, and not as an end point of a range. This more
326closely obeys the Principle of Least Astonishment. See
327L<perlrecharclass/Bracketed Character Classes>. Note that a bug [perl
328#89774], now fixed as part of this change, prevented the previous
329behavior from working fully.
330
331=head2 Explicit rules for variable names and identifiers
332
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333Due to an oversight, single character variable names in v5.16 were
334completely unrestricted. This opened the door to several kinds of
335insanity. As of v5.18, these now follow the rules of other identifiers,
336in addition to accepting characters that match the C<\p{POSIX_Punct}>
337property.
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338
339There are no longer any differences in the parsing of identifiers
340specified as C<$...> or C<${...}>; previously, they were dealt with in
341different parts of the core, and so had slightly different behavior. For
342instance, C<${foo:bar}> was a legal variable name. Since they are now
343both parsed by the same code, that is no longer the case.
344
345=head2 C<\s> in regular expressions now matches a Vertical Tab
346
347No one could recall why C<\s> didn't match C<\cK>, the vertical tab.
348Now it does. Given the extreme rarity of that character, very little
349breakage is expected.
350
351=head2 C</(?{})/> and C</(??{})/> have been heavily reworked
352
353The implementation of this feature has been almost completely rewritten.
354Although its main intent is to fix bugs, some behaviors, especially
355related to the scope of lexical variables, will have changed. This is
356described more fully in the L</Selected Bug Fixes> section.
357
358=head2 Stricter parsing of substitution replacement
359
360It is no longer possible to abuse the way the parser parses C<s///e> like
361this:
362
363 %_=(_,"Just another ");
364 $_="Perl hacker,\n";
365 s//_}->{_/e;print
366
367=head2 C<given> now aliases the global C<$_>
368
369Instead of assigning to an implicit lexical C<$_>, C<given> now makes the
370global C<$_> an alias for its argument, just like C<foreach>. However, it
371still uses lexical C<$_> if there is lexical C<$_> in scope (again, just like
372C<foreach>) [perl #114020].
373
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374=head2 The smartmatch family of features are now experimental
375
376Smart match, added in v5.10.0 and significantly revised in v5.10.1, has been
377a regular point of complaint. Although there are a number of ways in which
378it is useful, it has also proven problematic and confusing for both users and
379implementors of Perl. There have been a number of proposals on how to best
380address the problem. It is clear that smartmatch is almost certainly either
381going to change or go away in the future. Relying on its current behavior
382is not recommended.
383
384Warnings will now be issued when the parser sees C<~~>, C<given>, or C<when>.
385To disable these warnings, you can add this line to the appropriate scope:
386
387 no if $] >= 5.018, "experimental::smartmatch";
388
389Consider, though, replacing the use of these features, as they may change
390behavior again before becoming stable.
391
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392=head2 Lexical C<$_> is now experimental
393
e612b5a0 394Since it was introduced in Perl v5.10, it has caused much confusion with no
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395obvious solution:
396
397=over
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398
399=item *
400
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401Various modules (e.g., List::Util) expect callback routines to use the
402global C<$_>. C<use List::Util 'first'; my $_; first { $_ == 1 } @list>
403does not work as one would expect.
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404
405=item *
406
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407A C<my $_> declaration earlier in the same file can cause confusing closure
408warnings.
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409
410=item *
411
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412The "_" subroutine prototype character allows called subroutines to access
413your lexical C<$_>, so it is not really private after all.
2426c394 414
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415=item *
416
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417Nevertheless, subroutines with a "(@)" prototype and methods cannot access
418the caller's lexical C<$_>, unless they are written in XS.
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419
420=item *
421
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422But even XS routines cannot access a lexical C<$_> declared, not in the
423calling subroutine, but in an outer scope, iff that subroutine happened not
424to mention C<$_> or use any operators that default to C<$_>.
425
426=back
427
428It is our hope that lexical C<$_> can be rehabilitated, but this may
429cause changes in its behavior. Please use it with caution until it
430becomes stable.
431
432=head2 readline() with C<$/ = \N> now reads N characters, not N bytes
433
434Previously, when reading from a stream with I/O layers such as
435C<encoding>, the readline() function, otherwise known as the C<< <> >>
436operator, would read I<N> bytes from the top-most layer. [perl #79960]
437
438Now, I<N> characters are read instead.
439
440There is no change in behaviour when reading from streams with no
441extra layers, since bytes map exactly to characters.
442
443=head2 Overridden C<glob> is now passed one argument
444
445C<glob> overrides used to be passed a magical undocumented second argument
446that identified the caller. Nothing on CPAN was using this, and it got in
447the way of a bug fix, so it was removed. If you really need to identify
448the caller, see L<Devel::Callsite> on CPAN.
449
450=head2 Here-doc parsing
451
452The body of a here-document inside a quote-like operator now always begins
453on the line after the "<<foo" marker. Previously, it was documented to
454begin on the line following the containing quote-like operator, but that
455was only sometimes the case [perl #114040].
456
457=head2 Alphanumeric operators must now be separated from the closing
458delimiter of regular expressions
459
460You may no longer write something like:
461
462 m/a/and 1
463
464Instead you must write
465
466 m/a/ and 1
467
468with whitespace separating the operator from the closing delimiter of
469the regular expression. Not having whitespace has resulted in a
470deprecation warning since Perl v5.14.0.
471
472=head2 qw(...) can no longer be used as parentheses
473
474C<qw> lists used to fool the parser into thinking they were always
475surrounded by parentheses. This permitted some surprising constructions
476such as C<foreach $x qw(a b c) {...}>, which should really be written
477C<foreach $x (qw(a b c)) {...}>. These would sometimes get the lexer into
478the wrong state, so they didn't fully work, and the similar C<foreach qw(a
479b c) {...}> that one might expect to be permitted never worked at all.
480
481This side effect of C<qw> has now been abolished. It has been deprecated
e612b5a0 482since Perl v5.13.11. It is now necessary to use real parentheses
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483everywhere that the grammar calls for them.
484
485=head2 Interaction of lexical and default warnings
486
487Turning on any lexical warnings used first to disable all default warnings
488if lexical warnings were not already enabled:
489
490 $*; # deprecation warning
491 use warnings "void";
492 $#; # void warning; no deprecation warning
493
f105b7be 494Now, the C<debugging>, C<deprecated>, C<glob>, C<inplace> and C<malloc> warnings
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495categories are left on when turning on lexical warnings (unless they are
496turned off by C<no warnings>, of course).
497
498This may cause deprecation warnings to occur in code that used to be free
499of warnings.
500
501Those are the only categories consisting only of default warnings. Default
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502warnings in other categories are still disabled by C<< use warnings "category" >>,
503as we do not yet have the infrastructure for controlling
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504individual warnings.
505
506=head2 C<state sub> and C<our sub>
507
508Due to an accident of history, C<state sub> and C<our sub> were equivalent
509to a plain C<sub>, so one could even create an anonymous sub with
510C<our sub { ... }>. These are now disallowed outside of the "lexical_subs"
511feature. Under the "lexical_subs" feature they have new meanings described
512in L<perlsub/Lexical Subroutines>.
513
514=head2 Defined values stored in environment are forced to byte strings
515
516A value stored in an environment variable has always been stringified. In this
4f5e76eb 517release, it is converted to be only a byte string. First, it is forced to be
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518only a string. Then if the string is utf8 and the equivalent of
519C<utf8::downgrade()> works, that result is used; otherwise, the equivalent of
520C<utf8::encode()> is used, and a warning is issued about wide characters
521(L</Diagnostics>).
522
523=head2 C<require> dies for unreadable files
524
525When C<require> encounters an unreadable file, it now dies. It used to
526ignore the file and continue searching the directories in C<@INC>
527[perl #113422].
528
529=head2 C<gv_fetchmeth_*> and SUPER
530
531The various C<gv_fetchmeth_*> XS functions used to treat a package whose
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532named ended with C<::SUPER> specially. A method lookup on the C<Foo::SUPER>
533package would be treated as a C<SUPER> method lookup on the C<Foo> package. This
534is no longer the case. To do a C<SUPER> lookup, pass the C<Foo> stash and the
535C<GV_SUPER> flag.
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536
537=head2 C<split>'s first argument is more consistently interpreted
538
e612b5a0 539After some changes earlier in v5.17, C<split>'s behavior has been
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540simplified: if the PATTERN argument evaluates to a literal string
541containing one space, it is treated the way that a I<literal> string
542containing one space once was.
543
544=head1 Deprecations
545
546=head2 Deprecated modules
547
548The following modules will be removed from the core distribution in a
549future release, and should be installed from CPAN instead. Distributions
550on CPAN which require these should add them to their prerequisites.
f105b7be 551The core versions of these modules will issue C<"deprecated">-category
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552warnings.
553
554You can silence these deprecation warnings by installing the modules
555in question from CPAN.
556
557=over
558
559=item L<Archive::Extract>
560
561=item L<B::Lint>
562
563=item L<B::Lint::Debug>
564
565=item L<CPANPLUS> and all included C<CPANPLUS::*> modules
566
567=item L<Devel::InnerPackage>
568
569=item L<encoding>
570
571=item L<Log::Message>
572
573=item L<Log::Message::Config>
574
575=item L<Log::Message::Handlers>
576
577=item L<Log::Message::Item>
578
579=item L<Log::Message::Simple>
580
581=item L<Module::Pluggable>
582
583=item L<Module::Pluggable::Object>
584
585=item L<Object::Accessor>
586
587=item L<Pod::LaTeX>
588
589=item L<Term::UI>
590
591=item L<Term::UI::History>
592
593=back
594
595=head2 Deprecated Utilities
596
597The following utilities will be removed from the core distribution in a
598future release as their associated modules have been deprecated. They
599will remain available with the applicable CPAN distribution.
600
601=over
602
603=item L<cpanp>
604
605=item C<cpanp-run-perl>
606
607=item L<cpan2dist>
608
609These items are part of the C<CPANPLUS> distribution.
610
611=item L<pod2latex>
612
613This item is part of the C<Pod::LaTeX> distribution.
614
615=back
616
617=head2 PL_sv_objcount
618
619This interpreter-global variable used to track the total number of
620Perl objects in the interpreter. It is no longer maintained and will
e612b5a0 621be removed altogether in Perl v5.20.
5ed58cbd
RS
622
623=head2 Five additional characters should be escaped in patterns with C</x>
624
625When a regular expression pattern is compiled with C</x>, Perl treats 6
626characters as white space to ignore, such as SPACE and TAB. However,
627Unicode recommends 11 characters be treated thusly. We will conform
628with this in a future Perl version. In the meantime, use of any of the
629missing characters will raise a deprecation warning, unless turned off.
630The five characters are:
f105b7be 631
c163876c
RS
632 U+0085 NEXT LINE
633 U+200E LEFT-TO-RIGHT MARK
634 U+200F RIGHT-TO-LEFT MARK
635 U+2028 LINE SEPARATOR
636 U+2029 PARAGRAPH SEPARATOR
5ed58cbd
RS
637
638=head2 User-defined charnames with surprising whitespace
639
640A user-defined character name with trailing or multiple spaces in a row is
641likely a typo. This now generates a warning when defined, on the assumption
642that uses of it will be unlikely to include the excess whitespace.
643
644=head2 Various XS-callable functions are now deprecated
645
646All the functions used to classify characters will be removed from a
647future version of Perl, and should not be used. With participating C
648compilers (e.g., gcc), compiling any file that uses any of these will
649generate a warning. These were not intended for public use; there are
650equivalent, faster, macros for most of them.
e612b5a0 651
2e7bc647 652See L<perlapi/Character classes>. The complete list is:
e612b5a0 653
5ed58cbd
RS
654C<is_uni_alnum>, C<is_uni_alnumc>, C<is_uni_alnumc_lc>,
655C<is_uni_alnum_lc>, C<is_uni_alpha>, C<is_uni_alpha_lc>,
656C<is_uni_ascii>, C<is_uni_ascii_lc>, C<is_uni_blank>,
657C<is_uni_blank_lc>, C<is_uni_cntrl>, C<is_uni_cntrl_lc>,
658C<is_uni_digit>, C<is_uni_digit_lc>, C<is_uni_graph>,
659C<is_uni_graph_lc>, C<is_uni_idfirst>, C<is_uni_idfirst_lc>,
660C<is_uni_lower>, C<is_uni_lower_lc>, C<is_uni_print>,
661C<is_uni_print_lc>, C<is_uni_punct>, C<is_uni_punct_lc>,
662C<is_uni_space>, C<is_uni_space_lc>, C<is_uni_upper>,
663C<is_uni_upper_lc>, C<is_uni_xdigit>, C<is_uni_xdigit_lc>,
664C<is_utf8_alnum>, C<is_utf8_alnumc>, C<is_utf8_alpha>,
665C<is_utf8_ascii>, C<is_utf8_blank>, C<is_utf8_char>,
666C<is_utf8_cntrl>, C<is_utf8_digit>, C<is_utf8_graph>,
667C<is_utf8_idcont>, C<is_utf8_idfirst>, C<is_utf8_lower>,
668C<is_utf8_mark>, C<is_utf8_perl_space>, C<is_utf8_perl_word>,
669C<is_utf8_posix_digit>, C<is_utf8_print>, C<is_utf8_punct>,
670C<is_utf8_space>, C<is_utf8_upper>, C<is_utf8_xdigit>,
671C<is_utf8_xidcont>, C<is_utf8_xidfirst>.
672
673In addition these three functions that have never worked properly are
674deprecated:
675C<to_uni_lower_lc>, C<to_uni_title_lc>, and C<to_uni_upper_lc>.
676
f105b7be 677=head2 Certain rare uses of backslashes within regexes are now deprecated
5ed58cbd
RS
678
679There are three pairs of characters that Perl recognizes as
680metacharacters in regular expression patterns: C<{}>, C<[]>, and C<()>.
681These can be used as well to delimit patterns, as in:
682
683 m{foo}
684 s(foo)(bar)
685
686Since they are metacharacters, they have special meaning to regular
687expression patterns, and it turns out that you can't turn off that
688special meaning by the normal means of preceding them with a backslash,
f105b7be 689if you use them, paired, within a pattern delimited by them. For
5ed58cbd
RS
690example, in
691
692 m{foo\{1,3\}}
693
694the backslashes do not change the behavior, and this matches
695S<C<"f o">> followed by one to three more occurrences of C<"o">.
696
697Usages like this, where they are interpreted as metacharacters, are
698exceedingly rare; we think there are none, for example, in all of CPAN.
699Hence, this deprecation should affect very little code. It does give
700notice, however, that any such code needs to change, which will in turn
701allow us to change the behavior in future Perl versions so that the
702backslashes do have an effect, and without fear that we are silently
703breaking any existing code.
704
d5f315e8
KW
705=head2 Splitting the tokens C<(?> and C<(*> in regular expressions
706
707A deprecation warning is now raised if the C<(> and C<?> are separated
708by white space or comments in C<(?...)> regular expression constructs.
709Similarly, if the C<(> and C<*> are separated in C<(*VERB...)>
710constructs.
711
e0a1dec5
LT
712=head2 Pre-PerlIO IO implementations
713
f3068e1b
RS
714In theory, you can currently build perl without PerlIO. Instead, you'd use a
715wrapper around stdio or sfio. In practice, this isn't very useful. It's not
716well tested, and without any support for IO layers or (thus) Unicode, it's not
717much of a perl. Building without PerlIO will most likely be removed in the
718next version of perl.
719
720PerlIO supports a C<stdio> layer if stdio use is desired. Similarly a
721sfio layer could be produced in the future, if needed.
e0a1dec5 722
5ed58cbd
RS
723=head1 Future Deprecations
724
725=over
71e6aba6
RS
726
727=item *
728
4263dd11 729Platforms without support infrastructure
5ed58cbd
RS
730
731Both Windows CE and z/OS have been historically under-maintained, and are
732currently neither successfully building nor regularly being smoke tested.
733Efforts are underway to change this situation, but it should not be taken for
734granted that the platforms are safe and supported. If they do not become
735buildable and regularly smoked, support for them may be actively removed in
736future releases. If you have an interest in these platforms and you can lend
737your time, expertise, or hardware to help support these platforms, please let
738the perl development effort know by emailing C<perl5-porters@perl.org>.
739
740Some platforms that appear otherwise entirely dead are also on the short list
e612b5a0 741for removal between now and v5.20.0:
5ed58cbd
RS
742
743=over
744
745=item DG/UX
746
747=item NeXT
748
749=back
1993add8 750
ec985017
RS
751We also think it likely that current versions of Perl will no longer
752build AmigaOS, DJGPP, NetWare (natively), OS/2 and Plan 9. If you
753are using Perl on such a platform and have an interest in ensuring
754Perl's future on them, please contact us.
755
756We believe that Perl has long been unable to build on mixed endian
ad94908e 757architectures (such as PDP-11s), and intend to remove any remaining
ec985017
RS
758support code. Similarly, code supporting the long umaintained GNU
759dld will be removed soon if no-one makes themselves known as an
760active user.
761
1993add8
RS
762=item *
763
5ed58cbd
RS
764Swapping of $< and $>
765
766For more information about this future deprecation, see L<the relevant RT
767ticket|https://rt.perl.org/rt3/Ticket/Display.html?id=96212>.
71e6aba6
RS
768
769=item *
770
5ed58cbd 771C<microperl>, long broken and of unclear present purpose, will be removed.
71e6aba6
RS
772
773=item *
774
5ed58cbd
RS
775Revamping C<< "\Q" >> semantics in double-quotish strings when combined with
776other escapes.
777
778There are several bugs and inconsistencies involving combinations
779of C<\Q> and escapes like C<\x>, C<\L>, etc., within a C<\Q...\E> pair.
780These need to be fixed, and doing so will necessarily change current
781behavior. The changes have not yet been settled.
71e6aba6 782
d5f315e8
KW
783=item *
784
785Use of C<$^>, where C<^> stands for any actual (non-printing) C0 control
786character will be disallowed in a future Perl version. Use C<${^}>
787instead (where again C<^> stands for a control character),
788or better, C<$^A> , where C<^> this time is a caret (CIRCUMFLEX ACCENT),
789and C<A> stands for any of the characters listed at the end of
790L<perlebcdic/OPERATOR DIFFERENCES>.
791
337fb649 792=back
2426c394 793
5ed58cbd
RS
794=head1 Performance Enhancements
795
796=over 4
2426c394 797
5ed58cbd 798=item *
2426c394 799
5ed58cbd
RS
800Lists of lexical variable declarations (C<my($x, $y)>) are now optimised
801down to a single op and are hence faster than before.
2426c394 802
5ed58cbd 803=item *
2426c394 804
5ed58cbd
RS
805A new C preprocessor define C<NO_TAINT_SUPPORT> was added that, if set,
806disables Perl's taint support altogether. Using the -T or -t command
807line flags will cause a fatal error. Beware that both core tests as
808well as many a CPAN distribution's tests will fail with this change. On
809the upside, it provides a small performance benefit due to reduced
810branching.
2426c394 811
5ed58cbd
RS
812B<Do not enable this unless you know exactly what you are getting yourself
813into.>
814
815=item *
816
817C<pack> with constant arguments is now constant folded in most cases
818[perl #113470].
819
820=item *
821
822Speed up in regular expression matching against Unicode properties. The
823largest gain is for C<\X>, the Unicode "extended grapheme cluster." The
824gain for it is about 35% - 40%. Bracketed character classes, e.g.,
825C<[0-9\x{100}]> containing code points above 255 are also now faster.
826
827=item *
828
829On platforms supporting it, several former macros are now implemented as static
830inline functions. This should speed things up slightly on non-GCC platforms.
831
832=item *
833
66f62cf6
RS
834The optimisation of hashes in boolean context has been extended to
835affect C<scalar(%hash)>, C<%hash ? ... : ...>, and C<sub { %hash || ... }>.
5ed58cbd
RS
836
837=item *
838
f105b7be 839Filetest operators manage the stack in a fractionally more efficient manner.
5ed58cbd
RS
840
841=item *
842
843Globs used in a numeric context are now numified directly in most cases,
f105b7be 844rather than being numified via stringification.
5ed58cbd
RS
845
846=item *
847
848The C<x> repetition operator is now folded to a single constant at compile
849time if called in scalar context with constant operands and no parentheses
850around the left operand.
851
852=back
853
854=head1 Modules and Pragmata
855
856=head2 New Modules and Pragmata
2426c394 857
337fb649 858=over 4
982110e0 859
82d98f72 860=item *
2426c394 861
5ed58cbd
RS
862L<Config::Perl::V> version 0.16 has been added as a dual-lifed module.
863It provides structured data retrieval of C<perl -V> output including
864information only known to the C<perl> binary and not available via L<Config>.
865
866=back
867
868=head2 Updated Modules and Pragmata
869
9863976f 870For a complete list of updates, run:
5ed58cbd 871
f105b7be 872 $ corelist --diff 5.16.0 5.18.0
5ed58cbd 873
e612b5a0 874You can substitute your favorite version in place of C<5.16.0>, too.
5ed58cbd 875
357b01df
AAS
876=over
877
878=item *
879
606e21ea 880L<Archive::Extract> has been upgraded to 0.68.
357b01df
AAS
881
882Work around an edge case on Linux with Busybox's unzip.
883
884=item *
885
606e21ea 886L<Archive::Tar> has been upgraded to 1.90.
357b01df
AAS
887
888ptar now supports the -T option as well as dashless options
889[rt.cpan.org #75473], [rt.cpan.org #75475].
890
891Auto-encode filenames marked as UTF-8 [rt.cpan.org #75474].
892
893Don't use C<tell> on L<IO::Zlib> handles [rt.cpan.org #64339].
894
895Don't try to C<chown> on symlinks.
896
897=item *
898
606e21ea 899L<autodie> has been upgraded to 2.13.
357b01df
AAS
900
901C<autodie> now plays nicely with the 'open' pragma.
902
903=item *
904
606e21ea 905L<B> has been upgraded to 1.42.
357b01df
AAS
906
907The C<stashoff> method of COPs has been added. This provides access to an
908internal field added in perl 5.16 under threaded builds [perl #113034].
909
910C<B::COP::stashpv> now supports UTF-8 package names and embedded NULs.
911
912All C<CVf_*> and C<GVf_*>
913and more SV-related flag values are now provided as constants in the C<B::>
914namespace and available for export. The default export list has not changed.
915
916This makes the module work with the new pad API.
917
918=item *
919
606e21ea 920L<B::Concise> has been upgraded to 0.95.
357b01df
AAS
921
922The C<-nobanner> option has been fixed, and C<format>s can now be dumped.
923When passed a sub name to dump, it will check also to see whether it
924is the name of a format. If a sub and a format share the same name,
925it will dump both.
926
927This adds support for the new C<OpMAYBE_TRUEBOOL> and C<OPpTRUEBOOL> flags.
928
929=item *
930
606e21ea 931L<B::Debug> has been upgraded to 1.18.
357b01df
AAS
932
933This adds support (experimentally) for C<B::PADLIST>, which will be
934added in Perl 5.17.4.
935
936=item *
937
606e21ea 938L<B::Deparse> has been upgraded to 1.20.
357b01df
AAS
939
940Avoid warning when run under C<perl -w>.
941
942It now deparses
943loop controls with the correct precedence, and multiple statements in a
944C<format> line are also now deparsed correctly.
945
946This release suppresses trailing semicolons in formats.
947
948This release adds stub deparsing for lexical subroutines.
949
950It no longer dies when deparsing C<sort> without arguments. It now
951correctly omits the comma for C<system $prog @args> and C<exec $prog
952@args>.
953
954=item *
955
606e21ea 956L<bignum>, L<bigint> and L<bigrat> have been upgraded to 0.33.
357b01df
AAS
957
958The overrides for C<hex> and C<oct> have been rewritten, eliminating
959several problems, and making one incompatible change:
960
961=over
962
963=item *
964
965Formerly, whichever of C<use bigint> or C<use bigrat> was compiled later
966would take precedence over the other, causing C<hex> and C<oct> not to
967respect the other pragma when in scope.
968
969=item *
970
971Using any of these three pragmata would cause C<hex> and C<oct> anywhere
972else in the program to evalute their arguments in list context and prevent
973them from inferring $_ when called without arguments.
974
975=item *
976
977Using any of these three pragmata would make C<oct("1234")> return 1234
978(for any number not beginning with 0) anywhere in the program. Now "1234"
979is translated from octal to decimal, whether within the pragma's scope or
980not.
981
982=item *
983
984The global overrides that facilitate lexical use of C<hex> and C<oct> now
985respect any existing overrides that were in place before the new overrides
986were installed, falling back to them outside of the scope of C<use bignum>.
987
988=item *
989
990C<use bignum "hex">, C<use bignum "oct"> and similar invocations for bigint
991and bigrat now export a C<hex> or C<oct> function, instead of providing a
992global override.
993
994=back
995
996=item *
997
a0932e7e 998L<Carp> has been upgraded to 1.29.
357b01df
AAS
999
1000Carp is no longer confused when C<caller> returns undef for a package that
1001has been deleted.
1002
1003The C<longmess()> and C<shortmess()> functions are now documented.
1004
1005=item *
1006
606e21ea 1007L<CGI> has been upgraded to 3.63.
357b01df
AAS
1008
1009Unrecognized HTML escape sequences are now handled better, problematic
1010trailing newlines are no longer inserted after E<lt>formE<gt> tags
1011by C<startform()> or C<start_form()>, and bogus "Insecure Dependency"
1012warnings appearing with some versions of perl are now worked around.
1013
1014=item *
1015
606e21ea 1016L<Class::Struct> has been upgraded to 0.64.
357b01df
AAS
1017
1018The constructor now respects overridden accessor methods [perl #29230].
1019
1020=item *
1021
606e21ea 1022L<Compress::Raw::Bzip2> has been upgraded to 2.060.
357b01df
AAS
1023
1024The misuse of Perl's "magic" API has been fixed.
1025
1026=item *
1027
606e21ea 1028L<Compress::Raw::Zlib> has been upgraded to 2.060.
357b01df
AAS
1029
1030Upgrade bundled zlib to version 1.2.7.
1031
1032Fix build failures on Irix, Solaris, and Win32, and also when building as C++
1033[rt.cpan.org #69985], [rt.cpan.org #77030], [rt.cpan.org #75222].
1034
1035The misuse of Perl's "magic" API has been fixed.
1036
1037C<compress()>, C<uncompress()>, C<memGzip()> and C<memGunzip()> have
1038been speeded up by making parameter validation more efficient.
1039
1040=item *
1041
606e21ea 1042L<CPAN::Meta::Requirements> has been upgraded to 2.122.
357b01df
AAS
1043
1044Treat undef requirements to C<from_string_hash> as 0 (with a warning).
1045
1046Added C<requirements_for_module> method.
1047
1048=item *
1049
606e21ea 1050L<CPANPLUS> has been upgraded to 0.9135.
357b01df
AAS
1051
1052Allow adding F<blib/script> to PATH.
1053
1054Save the history between invocations of the shell.
1055
1056Handle multiple C<makemakerargs> and C<makeflags> arguments better.
1057
1058This resolves issues with the SQLite source engine.
1059
1060=item *
1061
606e21ea 1062L<Data::Dumper> has been upgraded to 2.145.
357b01df
AAS
1063
1064It has been optimized to only build a seen-scalar hash as necessary,
1065thereby speeding up serialization drastically.
1066
1067Additional tests were added in order to improve statement, branch, condition
1068and subroutine coverage. On the basis of the coverage analysis, some of the
1069internals of Dumper.pm were refactored. Almost all methods are now
1070documented.
1071
1072=item *
1073
606e21ea 1074L<DB_File> has been upgraded to 1.827.
357b01df
AAS
1075
1076The main Perl module no longer uses the C<"@_"> construct.
1077
1078=item *
1079
606e21ea 1080L<Devel::Peek> has been upgraded to 1.11.
357b01df
AAS
1081
1082This fixes compilation with C++ compilers and makes the module work with
1083the new pad API.
1084
1085=item *
1086
606e21ea 1087L<Digest::MD5> has been upgraded to 2.52.
357b01df
AAS
1088
1089Fix C<Digest::Perl::MD5> OO fallback [rt.cpan.org #66634].
1090
1091=item *
1092
606e21ea 1093L<Digest::SHA> has been upgraded to 5.84.
357b01df
AAS
1094
1095This fixes a double-free bug, which might have caused vulnerabilities
1096in some cases.
1097
1098=item *
1099
606e21ea 1100L<DynaLoader> has been upgraded to 1.18.
357b01df
AAS
1101
1102This is due to a minor code change in the XS for the VMS implementation.
1103
1104This fixes warnings about using C<CODE> sections without an C<OUTPUT>
1105section.
1106
1107=item *
1108
606e21ea 1109L<Encode> has been upgraded to 2.49.
357b01df
AAS
1110
1111The Mac alias x-mac-ce has been added, and various bugs have been fixed
1112in Encode::Unicode, Encode::UTF7 and Encode::GSM0338.
1113
1114=item *
1115
606e21ea 1116L<Env> has been upgraded to 1.04.
357b01df
AAS
1117
1118Its SPLICE implementation no longer misbehaves in list context.
1119
1120=item *
1121
606e21ea 1122L<ExtUtils::CBuilder> has been upgraded to 0.280210.
357b01df
AAS
1123
1124Manifest files are now correctly embedded for those versions of VC++ which
1125make use of them. [perl #111782, #111798].
1126
1127A list of symbols to export can now be passed to C<link()> when on
1128Windows, as on other OSes [perl #115100].
1129
1130=item *
1131
606e21ea 1132L<ExtUtils::ParseXS> has been upgraded to 3.18.
357b01df
AAS
1133
1134The generated C code now avoids unnecessarily incrementing
1135C<PL_amagic_generation> on Perl versions where it's done automatically
1136(or on current Perl where the variable no longer exists).
1137
1138This avoids a bogus warning for initialised XSUB non-parameters [perl
1139#112776].
1140
1141=item *
1142
606e21ea 1143L<File::Copy> has been upgraded to 2.26.
357b01df
AAS
1144
1145C<copy()> no longer zeros files when copying into the same directory,
1146and also now fails (as it has long been documented to do) when attempting
1147to copy a file over itself.
1148
1149=item *
1150
606e21ea 1151L<File::DosGlob> has been upgraded to 1.10.
357b01df
AAS
1152
1153The internal cache of file names that it keeps for each caller is now
1154freed when that caller is freed. This means
1155C<< use File::DosGlob 'glob'; eval 'scalar <*>' >> no longer leaks memory.
1156
1157=item *
1158
606e21ea 1159L<File::Fetch> has been upgraded to 0.38.
357b01df
AAS
1160
1161Added the 'file_default' option for URLs that do not have a file
1162component.
1163
1164Use C<File::HomeDir> when available, and provide C<PERL5_CPANPLUS_HOME> to
1165override the autodetection.
1166
1167Always re-fetch F<CHECKSUMS> if C<fetchdir> is set.
1168
1169=item *
1170
606e21ea 1171L<File::Find> has been upgraded to 1.23.
357b01df
AAS
1172
1173This fixes inconsistent unixy path handling on VMS.
1174
1175Individual files may now appear in list of directories to be searched
1176[perl #59750].
1177
1178=item *
1179
606e21ea 1180L<File::Glob> has been upgraded to 1.20.
357b01df
AAS
1181
1182File::Glob has had exactly the same fix as File::DosGlob. Since it is
1183what Perl's own C<glob> operator itself uses (except on VMS), this means
1184C<< eval 'scalar <*>' >> no longer leaks.
1185
1186A space-separated list of patterns return long lists of results no longer
1187results in memory corruption or crashes. This bug was introduced in
1188Perl 5.16.0. [perl #114984]
1189
1190=item *
1191
606e21ea 1192L<File::Spec::Unix> has been upgraded to 3.40.
357b01df
AAS
1193
1194C<abs2rel> could produce incorrect results when given two relative paths or
1195the root directory twice [perl #111510].
1196
1197=item *
1198
606e21ea 1199L<File::stat> has been upgraded to 1.07.
357b01df
AAS
1200
1201C<File::stat> ignores the L<filetest> pragma, and warns when used in
1202combination therewith. But it was not warning for C<-r>. This has been
1203fixed [perl #111640].
1204
1205C<-p> now works, and does not return false for pipes [perl #111638].
1206
1207Previously C<File::stat>'s overloaded C<-x> and C<-X> operators did not give
1208the correct results for directories or executable files when running as
1209root. They had been treating executable permissions for root just like for
1210any other user, performing group membership tests I<etc> for files not owned
1211by root. They now follow the correct Unix behaviour - for a directory they
1212are always true, and for a file if any of the three execute permission bits
1213are set then they report that root can execute the file. Perl's builtin
1214C<-x> and C<-X> operators have always been correct.
1215
1216=item *
1217
606e21ea 1218L<File::Temp> has been upgraded to 0.23
357b01df
AAS
1219
1220Fixes various bugs involving directory removal. Defers unlinking tempfiles if
1221the initial unlink fails, which fixes problems on NFS.
1222
1223=item *
1224
606e21ea 1225L<GDBM_File> has been upgraded to 1.15.
357b01df
AAS
1226
1227The undocumented optional fifth parameter to C<TIEHASH> has been
1228removed. This was intended to provide control of the callback used by
1229C<gdbm*> functions in case of fatal errors (such as filesystem problems),
1230but did not work (and could never have worked). No code on CPAN even
1231attempted to use it. The callback is now always the previous default,
1232C<croak>. Problems on some platforms with how the C<C> C<croak> function
1233is called have also been resolved.
1234
1235=item *
1236
606e21ea 1237L<Hash::Util> has been upgraded to 0.15.
357b01df
AAS
1238
1239C<hash_unlocked> and C<hashref_unlocked> now returns true if the hash is
1240unlocked, instead of always returning false [perl #112126].
1241
1242C<hash_unlocked>, C<hashref_unlocked>, C<lock_hash_recurse> and
1243C<unlock_hash_recurse> are now exportable [perl #112126].
1244
1245Two new functions, C<hash_locked> and C<hashref_locked>, have been added.
1246Oddly enough, these two functions were already exported, even though they
1247did not exist [perl #112126].
1248
1249=item *
1250
606e21ea 1251L<HTTP::Tiny> has been upgraded to 0.025.
357b01df
AAS
1252
1253Add SSL verification features [github #6], [github #9].
1254
1255Include the final URL in the response hashref.
1256
1257Add C<local_address> option.
1258
1259This improves SSL support.
1260
1261=item *
1262
606e21ea 1263L<IO> has been upgraded to 1.28.
357b01df
AAS
1264
1265C<sync()> can now be called on read-only file handles [perl #64772].
1266
1267L<IO::Socket> tries harder to cache or otherwise fetch socket
1268information.
1269
1270=item *
1271
606e21ea 1272L<IPC::Cmd> has been upgraded to 0.80.
357b01df
AAS
1273
1274Use C<POSIX::_exit> instead of C<exit> in C<run_forked> [rt.cpan.org #76901].
1275
1276=item *
1277
606e21ea 1278L<IPC::Open3> has been upgraded to 1.13.
357b01df
AAS
1279
1280The C<open3()> function no longer uses C<POSIX::close()> to close file
1281descriptors since that breaks the ref-counting of file descriptors done by
1282PerlIO in cases where the file descriptors are shared by PerlIO streams,
1283leading to attempts to close the file descriptors a second time when
1284any such PerlIO streams are closed later on.
1285
1286=item *
1287
606e21ea 1288L<Locale::Codes> has been upgraded to 3.25.
357b01df
AAS
1289
1290It includes some new codes.
1291
1292=item *
1293
606e21ea 1294L<Memoize> has been upgraded to 1.03.
357b01df
AAS
1295
1296Fix the C<MERGE> cache option.
1297
1298=item *
1299
606e21ea 1300L<Module::Build> has been upgraded to 0.4003.
357b01df
AAS
1301
1302Fixed bug where modules without C<$VERSION> might have a version of '0' listed
1303in 'provides' metadata, which will be rejected by PAUSE.
1304
1305Fixed bug in PodParser to allow numerals in module names.
1306
1307Fixed bug where giving arguments twice led to them becoming arrays, resulting
1308in install paths like F<ARRAY(0xdeadbeef)/lib/Foo.pm>.
1309
1310A minor bug fix allows markup to be used around the leading "Name" in
1311a POD "abstract" line, and some documentation improvements have been made.
1312
1313=item *
1314
606e21ea 1315L<Module::CoreList> has been upgraded to 2.90
357b01df
AAS
1316
1317Version information is now stored as a delta, which greatly reduces the
1318size of the F<CoreList.pm> file.
1319
1320This restores compatibility with older versions of perl and cleans up
1321the corelist data for various modules.
1322
1323=item *
1324
606e21ea 1325L<Module::Load::Conditional> has been upgraded to 0.54.
357b01df
AAS
1326
1327Fix use of C<requires> on perls installed to a path with spaces.
1328
1329Various enhancements include the new use of Module::Metadata.
1330
1331=item *
1332
606e21ea 1333L<Module::Metadata> has been upgraded to 1.000011.
357b01df
AAS
1334
1335The creation of a Module::Metadata object for a typical module file has
1336been sped up by about 40%, and some spurious warnings about C<$VERSION>s
1337have been suppressed.
1338
1339=item *
1340
606e21ea 1341L<Module::Pluggable> has been upgraded to 4.7.
357b01df
AAS
1342
1343Amongst other changes, triggers are now allowed on events, which gives
1344a powerful way to modify behaviour.
1345
1346=item *
1347
606e21ea 1348L<Net::Ping> has been upgraded to 2.41.
357b01df
AAS
1349
1350This fixes some test failures on Windows.
1351
1352=item *
1353
606e21ea 1354L<Opcode> has been upgraded to 1.25.
357b01df
AAS
1355
1356Reflect the removal of the boolkeys opcode and the addition of the
1357clonecv, introcv and padcv opcodes.
1358
1359=item *
1360
606e21ea 1361L<overload> has been upgraded to 1.22.
357b01df
AAS
1362
1363C<no overload> now warns for invalid arguments, just like C<use overload>.
1364
1365=item *
1366
606e21ea 1367L<PerlIO::encoding> has been upgraded to 0.16.
357b01df
AAS
1368
1369This is the module implementing the ":encoding(...)" I/O layer. It no
1370longer corrupts memory or crashes when the encoding back-end reallocates
1371the buffer or gives it a typeglob or shared hash key scalar.
1372
1373=item *
1374
606e21ea 1375L<PerlIO::scalar> has been upgraded to 0.16.
357b01df
AAS
1376
1377The buffer scalar supplied may now only contain code pounts 0xFF or
1378lower. [perl #109828]
1379
1380=item *
1381
606e21ea 1382L<Perl::OSType> has been upgraded to 1.003.
357b01df
AAS
1383
1384This fixes a bug detecting the VOS operating system.
1385
1386=item *
1387
606e21ea 1388L<Pod::Html> has been upgraded to 1.18.
357b01df
AAS
1389
1390The option C<--libpods> has been reinstated. It is deprecated, and its use
1391does nothing other than issue a warning that it is no longer supported.
1392
1393Since the HTML files generated by pod2html claim to have a UTF-8 charset,
1394actually write the files out using UTF-8 [perl #111446].
1395
1396=item *
1397
606e21ea 1398L<Pod::Simple> has been upgraded to 3.28.
357b01df
AAS
1399
1400Numerous improvements have been made, mostly to Pod::Simple::XHTML,
1401which also has a compatibility change: the C<codes_in_verbatim> option
1402is now disabled by default. See F<cpan/Pod-Simple/ChangeLog> for the
1403full details.
1404
1405=item *
1406
606e21ea 1407L<re> has been upgraded to 0.23
357b01df
AAS
1408
1409Single character [class]es like C</[s]/> or C</[s]/i> are now optimized
1410as if they did not have the brackets, i.e. C</s/> or C</s/i>.
1411
1412See note about C<op_comp> in the L</Internal Changes> section below.
1413
1414=item *
1415
606e21ea 1416L<Safe> has been upgraded to 2.35.
357b01df
AAS
1417
1418Fix interactions with C<Devel::Cover>.
1419
1420Don't eval code under C<no strict>.
1421
1422=item *
1423
606e21ea 1424L<Scalar::Util> has been upgraded to version 1.27.
357b01df
AAS
1425
1426Fix an overloading issue with C<sum>.
1427
1428C<first> and C<reduce> now check the callback first (so C<&first(1)> is
1429disallowed).
1430
1431Fix C<tainted> on magical values [rt.cpan.org #55763].
1432
1433Fix C<sum> on previously magical values [rt.cpan.org #61118].
1434
1435Fix reading past the end of a fixed buffer [rt.cpan.org #72700].
1436
1437=item *
1438
606e21ea 1439L<Search::Dict> has been upgraded to 1.07.
357b01df
AAS
1440
1441No longer require C<stat> on filehandles.
1442
1443Use C<fc> for casefolding.
1444
1445=item *
1446
606e21ea 1447L<Socket> has been upgraded to 2.009.
357b01df
AAS
1448
1449Constants and functions required for IP multicast source group membership
1450have been added.
1451
1452C<unpack_sockaddr_in()> and C<unpack_sockaddr_in6()> now return just the IP
1453address in scalar context, and C<inet_ntop()> now guards against incorrect
1454length scalars being passed in.
1455
1456This fixes an uninitialized memory read.
1457
1458=item *
1459
606e21ea 1460L<Storable> has been upgraded to 2.41.
357b01df
AAS
1461
1462Modifying C<$_[0]> within C<STORABLE_freeze> no longer results in crashes
1463[perl #112358].
1464
1465An object whose class implements C<STORABLE_attach> is now thawed only once
1466when there are multiple references to it in the structure being thawed
1467[perl #111918].
1468
1469Restricted hashes were not always thawed correctly [perl #73972].
1470
1471Storable would croak when freezing a blessed REF object with a
1472C<STORABLE_freeze()> method [perl #113880].
1473
1474It can now freeze and thaw vstrings correctly. This causes a slight
1475incompatible change in the storage format, so the format version has
1476increased to 2.9.
1477
1478This contains various bugfixes, including compatibility fixes for older
1479versions of Perl and vstring handling.
1480
1481=item *
1482
606e21ea 1483L<Sys::Syslog> has been upgraded to 0.32.
357b01df
AAS
1484
1485This contains several bug fixes relating to C<getservbyname()>,
1486C<setlogsock()>and log levels in C<syslog()>, together with fixes for
1487Windows, Haiku-OS and GNU/kFreeBSD. See F<cpan/Sys-Syslog/Changes>
1488for the full details.
1489
1490=item *
1491
606e21ea 1492L<Term::ANSIColor> has been upgraded to 4.02.
357b01df
AAS
1493
1494Add support for italics.
1495
1496Improve error handling.
1497
1498=item *
1499
606e21ea 1500L<Term::ReadLine> has been upgraded to 1.10. This fixes the
357b01df
AAS
1501use of the B<cpan> and B<cpanp> shells on Windows in the event that the current
1502drive happens to contain a F<\dev\tty> file.
1503
1504=item *
1505
606e21ea 1506L<Test::Harness> has been upgraded to 3.26.
357b01df
AAS
1507
1508Fix glob semantics on Win32 [rt.cpan.org #49732].
1509
1510Don't use C<Win32::GetShortPathName> when calling perl [rt.cpan.org #47890].
1511
1512Ignore -T when reading shebang [rt.cpan.org #64404].
1513
1514Handle the case where we don't know the wait status of the test more
1515gracefully.
1516
1517Make the test summary 'ok' line overridable so that it can be changed to a
1518plugin to make the output of prove idempotent.
1519
1520Don't run world-writable files.
1521
1522=item *
1523
606e21ea 1524L<Text::Tabs> and L<Text::Wrap> have been upgraded to
357b01df
AAS
15252012.0818. Support for Unicode combining characters has been added to them
1526both.
1527
1528=item *
1529
606e21ea 1530L<threads::shared> has been upgraded to 1.31.
357b01df
AAS
1531
1532This adds the option to warn about or ignore attempts to clone structures
1533that can't be cloned, as opposed to just unconditionally dying in
1534that case.
1535
1536This adds support for dual-valued values as created by
1537L<Scalar::Util::dualvar|Scalar::Util/"dualvar NUM, STRING">.
1538
1539=item *
1540
606e21ea 1541L<Tie::StdHandle> has been upgraded to 4.3.
357b01df
AAS
1542
1543C<READ> now respects the offset argument to C<read> [perl #112826].
1544
1545=item *
1546
606e21ea 1547L<Time::Local> has been upgraded to 1.2300.
357b01df
AAS
1548
1549Seconds values greater than 59 but less than 60 no longer cause
1550C<timegm()> and C<timelocal()> to croak.
1551
1552=item *
1553
606e21ea 1554L<Unicode::UCD> has been upgraded to 0.53.
357b01df
AAS
1555
1556This adds a function L<all_casefolds()|Unicode::UCD/all_casefolds()>
1557that returns all the casefolds.
1558
1559=item *
1560
606e21ea 1561L<Win32> has been upgraded to 0.47.
357b01df
AAS
1562
1563New APIs have been added for getting and setting the current code page.
1564
1565=back
1566
1567
5ed58cbd
RS
1568=head2 Removed Modules and Pragmata
1569
32b79602 1570=over
33392251
BF
1571
1572=item *
1573
5ed58cbd
RS
1574L<Version::Requirements> has been removed from the core distribution. It is
1575available under a different name: L<CPAN::Meta::Requirements>.
2426c394 1576
337fb649 1577=back
2426c394 1578
5ed58cbd 1579=head1 Documentation
19718730 1580
5ed58cbd
RS
1581=head2 Changes to Existing Documentation
1582
1583=head3 L<perlcheat>
82d98f72 1584
5a6a30f4 1585=over 4
b7c7d786 1586
5ed58cbd
RS
1587=item *
1588
1589L<perlcheat> has been reorganized, and a few new sections were added.
1590
1591=back
1592
1593=head3 L<perldata>
1594
1595=over 4
82d98f72 1596
5ed58cbd 1597=item *
d2d1e842 1598
5ed58cbd
RS
1599Now explicitly documents the behaviour of hash initializer lists that
1600contain duplicate keys.
f355e93d 1601
5a6a30f4 1602=back
f355e93d 1603
5ed58cbd 1604=head3 L<perldiag>
19718730 1605
19718730 1606=over 4
e14ac59b 1607
5ed58cbd
RS
1608=item *
1609
1610The explanation of symbolic references being prevented by "strict refs"
1611now doesn't assume that the reader knows what symbolic references are.
1612
1613=back
9f351b45 1614
5ed58cbd 1615=head3 L<perlfaq>
9f351b45 1616
5ed58cbd 1617=over 4
9f351b45 1618
5ed58cbd 1619=item *
7cf3104f 1620
5ed58cbd 1621L<perlfaq> has been synchronized with version 5.0150040 from CPAN.
12719193 1622
6253ee75 1623=back
216cf7fc 1624
5ed58cbd 1625=head3 L<perlfunc>
f5b73711 1626
5ed58cbd
RS
1627=over 4
1628
1629=item *
a75569c0 1630
5ed58cbd 1631The return value of C<pipe> is now documented.
a75569c0 1632
5ed58cbd 1633=item *
a75569c0 1634
5ed58cbd
RS
1635Clarified documentation of C<our>.
1636
1637=back
1638
1639=head3 L<perlop>
1640
1641=over 4
1642
1643=item *
1644
1645Loop control verbs (C<dump>, C<goto>, C<next>, C<last> and C<redo>) have always
1646had the same precedence as assignment operators, but this was not documented
1647until now.
1648
1649=back
1650
1651=head3 Diagnostics
1652
1653The following additions or changes have been made to diagnostic output,
1654including warnings and fatal error messages. For the complete list of
1655diagnostic messages, see L<perldiag>.
1656
5ed58cbd
RS
1657=head2 New Diagnostics
1658
5ed58cbd
RS
1659=head3 New Errors
1660
1661=over 4
1662
1663=item *
1664
1665L<Unterminated delimiter for here document|perldiag/"Unterminated delimiter for here document">
1666
1667This message now occurs when a here document label has an initial quotation
1668mark but the final quotation mark is missing.
1669
1670This replaces a bogus and misleading error message about not finding the label
1671itself [perl #114104].
1672
1673=item *
1674
1675L<panic: child pseudo-process was never scheduled|perldiag/"panic: child pseudo-process was never scheduled">
1676
1677This error is thrown when a child pseudo-process in the ithreads implementation
1678on Windows was not scheduled within the time period allowed and therefore was
1679not able to initialize properly [perl #88840].
1680
1681=item *
1682
1683L<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/">
1684
1685This error has been added for C<(?&0)>, which is invalid. It used to
1686produce an incomprehensible error message [perl #101666].
1687
1688=item *
1689
1690L<Can't use an undefined value as a subroutine reference|perldiag/"Can't use an undefined value as %s reference">
1691
1692Calling an undefined value as a subroutine now produces this error message.
1693It used to, but was accidentally disabled, first in Perl 5.004 for
e612b5a0 1694non-magical variables, and then in Perl v5.14 for magical (e.g., tied)
5ed58cbd
RS
1695variables. It has now been restored. In the mean time, undef was treated
1696as an empty string [perl #113576].
1697
1698=item *
1699
1700L<Experimental "%s" subs not enabled|perldiag/"Experimental "%s" subs not enabled">
1701
1702To use lexical subs, you must first enable them:
1703
1704 no warnings 'experimental::lexical_subs';
1705 use feature 'lexical_subs';
1706 my sub foo { ... }
1707
1708=back
1709
1710=head3 New Warnings
1711
1712=over 4
1713
1714=item *
1715
5ed58cbd
RS
1716Strings with code points over 0xFF may not be mapped into in-memory file
1717handles
1718
1719=item *
1720
1721L<'%s' resolved to '\o{%s}%d'|perldiag/"'%s' resolved to '\o{%s}%d'">
1722
1723=item *
1724
1725L<'Trailing white-space in a charnames alias definition is deprecated'|perldiag/"Trailing white-space in a charnames alias definition is deprecated">
1726
1727=item *
1728
1729L<'A sequence of multiple spaces in a charnames alias definition is deprecated'|perldiag/"A sequence of multiple spaces in a charnames alias definition is deprecated">
1730
1731=item *
1732
1733L<'Passing malformed UTF-8 to "%s" is deprecated'|perldiag/"Passing malformed UTF-8 to "%s" is deprecated">
1734
1735=item *
1736
1737L<Subroutine "&%s" is not available|perldiag/"Subroutine "&%s" is not available">
1738
1739(W closure) During compilation, an inner named subroutine or eval is
1740attempting to capture an outer lexical subroutine that is not currently
1741available. This can happen for one of two reasons. First, the lexical
1742subroutine may be declared in an outer anonymous subroutine that has not
1743yet been created. (Remember that named subs are created at compile time,
1744while anonymous subs are created at run-time.) For example,
1745
1746 sub { my sub a {...} sub f { \&a } }
1747
1748At the time that f is created, it can't capture the current the "a" sub,
1749since the anonymous subroutine hasn't been created yet. Conversely, the
1750following won't give a warning since the anonymous subroutine has by now
1751been created and is live:
1752
1753 sub { my sub a {...} eval 'sub f { \&a }' }->();
1754
1755The second situation is caused by an eval accessing a variable that has
1756gone out of scope, for example,
1757
1758 sub f {
1759 my sub a {...}
1760 sub { eval '\&a' }
1761 }
1762 f()->();
1763
1764Here, when the '\&a' in the eval is being compiled, f() is not currently
1765being executed, so its &a is not available for capture.
1766
1767=item *
1768
1769L<"%s" subroutine &%s masks earlier declaration in same %s|perldiag/"%s" subroutine &%s masks earlier declaration in same %s>
1770
1771(W misc) A "my" or "state" subroutine has been redeclared in the
1772current scope or statement, effectively eliminating all access to
1773the previous instance. This is almost always a typographical error.
1774Note that the earlier subroutine will still exist until the end of
1775the scope or until all closure references to it are destroyed.
1776
1777=item *
1778
1779L<The %s feature is experimental|perldiag/"The %s feature is experimental">
1780
1781(S experimental) This warning is emitted if you enable an experimental
1782feature via C<use feature>. Simply suppress the warning if you want
1783to use the feature, but know that in doing so you are taking the risk
1784of using an experimental feature which may change or be removed in a
1785future Perl version:
1786
1787 no warnings "experimental::lexical_subs";
1788 use feature "lexical_subs";
1789
1790=item *
1791
1792L<sleep(%u) too large|perldiag/"sleep(%u) too large">
1793
1794(W overflow) You called C<sleep> with a number that was larger than it can
1795reliably handle and C<sleep> probably slept for less time than requested.
1796
1797=item *
1798
1799L<Wide character in setenv|perldiag/"Wide character in %s">
1800
1801Attempts to put wide characters into environment variables via C<%ENV> now
1802provoke this warning.
1803
1804=item *
1805
1806"L<Invalid negative number (%s) in chr|perldiag/"Invalid negative number (%s) in chr">"
1807
1808C<chr()> now warns when passed a negative value [perl #83048].
1809
1810=item *
1811
1812"L<Integer overflow in srand|perldiag/"Integer overflow in srand">"
1813
1814C<srand()> now warns when passed a value that doesn't fit in a C<UV> (since the
1815value will be truncated rather than overflowing) [perl #40605].
1816
1817=item *
1818
1819"L<-i used with no filenames on the command line, reading from STDIN|perldiag/"-i used with no filenames on the command line, reading from STDIN">"
1820
1821Running perl with the C<-i> flag now warns if no input files are provided on
1822the command line [perl #113410].
1823
1824=back
1825
1826=head2 Changes to Existing Diagnostics
1827
1828=over 4
1829
1830=item *
1831
1832L<$* is no longer supported|perldiag/"$* is no longer supported">
1833
1834The warning that use of C<$*> and C<$#> is no longer supported is now
1835generated for every location that references them. Previously it would fail
1836to be generated if another variable using the same typeglob was seen first
1837(e.g. C<@*> before C<$*>), and would not be generated for the second and
1838subsequent uses. (It's hard to fix the failure to generate warnings at all
1839without also generating them every time, and warning every time is
1840consistent with the warnings that C<$[> used to generate.)
1841
1842=item *
1843
1844The warnings for C<\b{> and C<\B{> were added. They are a deprecation
1845warning which should be turned off by that category. One should not
1846have to turn off regular regexp warnings as well to get rid of these.
1847
1848=item *
1849
1850L<Constant(%s): Call to &{$^H{%s}} did not return a defined value|perldiag/Constant(%s): Call to &{$^H{%s}} did not return a defined value>
1851
1852Constant overloading that returns C<undef> results in this error message.
1853For numeric constants, it used to say "Constant(undef)". "undef" has been
1854replaced with the number itself.
1855
1856=item *
1857
1858The error produced when a module cannot be loaded now includes a hint that
1859the module may need to be installed: "Can't locate hopping.pm in @INC (you
1860may need to install the hopping module) (@INC contains: ...)"
1861
1862=item *
1863
1864L<vector argument not supported with alpha versions|perldiag/vector argument not supported with alpha versions>
1865
1866This warning was not suppressable, even with C<no warnings>. Now it is
1867suppressible, and has been moved from the "internal" category to the
1868"printf" category.
1869
1870=item *
1871
1872C<< Can't do {n,m} with n > m in regex; marked by <-- HERE in m/%s/ >>
1873
1874This fatal error has been turned into a warning that reads:
1875
1876L<< Quantifier {n,m} with n > m can't match in regex | perldiag/Quantifier {n,m} with n > m can't match in regex >>
1877
1878(W regexp) Minima should be less than or equal to maxima. If you really want
1879your regexp to match something 0 times, just put {0}.
1880
1881=item *
1882
1883The "Runaway prototype" warning that occurs in bizarre cases has been
1884removed as being unhelpful and inconsistent.
1885
1886=item *
1887
1888The "Not a format reference" error has been removed, as the only case in
1889which it could be triggered was a bug.
1890
1891=item *
1892
1893The "Unable to create sub named %s" error has been removed for the same
1894reason.
1895
1896=item *
1897
1898The 'Can't use "my %s" in sort comparison' error has been downgraded to a
1899warning, '"my %s" used in sort comparison' (with 'state' instead of 'my'
1900for state variables). In addition, the heuristics for guessing whether
1901lexical $a or $b has been misused have been improved to generate fewer
1902false positives. Lexical $a and $b are no longer disallowed if they are
1903outside the sort block. Also, a named unary or list operator inside the
1904sort block no longer causes the $a or $b to be ignored [perl #86136].
1905
1906=back
1907
1908=head1 Utility Changes
1909
1910=head3 L<h2xs>
1911
1912=over 4
1913
1914=item *
1915
1916F<h2xs> no longer produces invalid code for empty defines. [perl #20636]
1917
1918=back
1919
1920=head1 Configuration and Compilation
1921
1922=over 4
1923
1924=item *
1925
1926Added C<useversionedarchname> option to Configure
1927
1928When set, it includes 'api_versionstring' in 'archname'. E.g.
1929x86_64-linux-5.13.6-thread-multi. It is unset by default.
1930
1931This feature was requested by Tim Bunce, who observed that
f105b7be 1932C<INSTALL_BASE> creates a library structure that does not
5ed58cbd
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1933differentiate by perl version. Instead, it places architecture
1934specific files in "$install_base/lib/perl5/$archname". This makes
f105b7be 1935it difficult to use a common C<INSTALL_BASE> library path with
5ed58cbd
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1936multiple versions of perl.
1937
f105b7be 1938By setting C<-Duseversionedarchname>, the $archname will be
c2959982 1939distinct for architecture I<and> API version, allowing mixed use of
f105b7be 1940C<INSTALL_BASE>.
5ed58cbd
RS
1941
1942=item *
1943
ff772877
RS
1944Add a C<PERL_NO_INLINE_FUNCTIONS> option
1945
f105b7be 1946If C<PERL_NO_INLINE_FUNCTIONS> is defined, don't include "inline.h"
ff772877
RS
1947
1948This permits test code to include the perl headers for definitions without
1949creating a link dependency on the perl library (which may not exist yet).
1950
1951=item *
1952
5ed58cbd
RS
1953Configure will honour the external C<MAILDOMAIN> environment variable, if set.
1954
1955=item *
1956
1957C<installman> no longer ignores the silent option
1958
1959=item *
1960
1961Both C<META.yml> and C<META.json> files are now included in the distribution.
1962
1963=item *
1964
1965F<Configure> will now correctly detect C<isblank()> when compiling with a C++
1966compiler.
1967
1968=item *
1969
1970The pager detection in F<Configure> has been improved to allow responses which
1971specify options after the program name, e.g. B</usr/bin/less -R>, if the user
1972accepts the default value. This helps B<perldoc> when handling ANSI escapes
1973[perl #72156].
1974
1975=back
1976
1977=head1 Testing
1978
1979=over 4
1980
1981=item *
1982
1983The test suite now has a section for tests that require very large amounts
1984of memory. These tests won't run by default; they can be enabled by
1985setting the C<PERL_TEST_MEMORY> environment variable to the number of
1986gibibytes of memory that may be safely used.
1987
1988=back
1989
1990=head1 Platform Support
1991
1992=head2 Discontinued Platforms
1993
1994=over 4
1995
1996=item BeOS
1997
1998BeOS was an operating system for personal computers developed by Be Inc,
1999initially for their BeBox hardware. The OS Haiku was written as an open
2000source replacement for/continuation of BeOS, and its perl port is current and
2001actively maintained.
2002
2003=item UTS Global
2004
2005Support code relating to UTS global has been removed. UTS was a mainframe
2006version of System V created by Amdahl, subsequently sold to UTS Global. The
e612b5a0 2007port has not been touched since before Perl v5.8.0, and UTS Global is now
5ed58cbd
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2008defunct.
2009
2010=item VM/ESA
2011
2012Support for VM/ESA has been removed. The port was tested on 2.3.0, which
2013IBM ended service on in March 2002. 2.4.0 ended service in June 2003, and
2014was superseded by Z/VM. The current version of Z/VM is V6.2.0, and scheduled
2015for end of service on 2015/04/30.
2016
2017=item MPE/IX
2018
2019Support for MPE/IX has been removed.
2020
2021=item EPOC
2022
2023Support code relating to EPOC has been removed. EPOC was a family of
2024operating systems developed by Psion for mobile devices. It was the
2025predecessor of Symbian. The port was last updated in April 2002.
2026
2027=item Rhapsody
2028
2029Support for Rhapsody has been removed.
2030
2031=back
2032
2033=head2 Platform-Specific Notes
2034
2035=head3 AIX
2036
2037Configure now always adds C<-qlanglvl=extc99> to the CC flags on AIX when
2038using xlC. This will make it easier to compile a number of XS-based modules
2039that assume C99 [perl #113778].
2040
2041=head3 clang++
2042
2043There is now a workaround for a compiler bug that prevented compiling
e612b5a0 2044with clang++ since Perl v5.15.7 [perl #112786].
5ed58cbd
RS
2045
2046=head3 C++
2047
2048When compiling the Perl core as C++ (which is only semi-supported), the
2049mathom functions are now compiled as C<extern "C">, to ensure proper
2050binary compatibility. (However, binary compatibility isn't generally
2051guaranteed anyway in the situations where this would matter.)
2052
2053=head3 Darwin
2054
2055Stop hardcoding an alignment on 8 byte boundaries to fix builds using
2056-Dusemorebits.
2057
2058=head3 Haiku
2059
2060Perl should now work out of the box on Haiku R1 Alpha 4.
2061
2062=head3 MidnightBSD
2063
2064C<libc_r> was removed from recent versions of MidnightBSD and older versions
2065work better with C<pthread>. Threading is now enabled using C<pthread> which
2066corrects build errors with threading enabled on 0.4-CURRENT.
2067
2068=head3 Solaris
2069
2070In Configure, avoid running sed commands with flags not supported on Solaris.
2071
2072=head3 VMS
2073
2074=over
2075
2076=item *
2077
2078Where possible, the case of filenames and command-line arguments is now
2079preserved by enabling the CRTL features C<DECC$EFS_CASE_PRESERVE> and
2080C<DECC$ARGV_PARSE_STYLE> at start-up time. The latter only takes effect
2081when extended parse is enabled in the process from which Perl is run.
2082
2083=item *
2084
2085The character set for Extended Filename Syntax (EFS) is now enabled by default
2086on VMS. Among other things, this provides better handling of dots in directory
05f5908f 2087names, multiple dots in filenames, and spaces in filenames. To obtain the old
5ed58cbd
RS
2088behavior, set the logical name C<DECC$EFS_CHARSET> to C<DISABLE>.
2089
2090=item *
2091
05f5908f 2092Fixed linking on builds configured with C<-Dusemymalloc=y>.
5ed58cbd
RS
2093
2094=item *
2095
05f5908f
CB
2096Experimental support for building Perl with the HP C++ compiler is available
2097by configuring with C<-Dusecxx>.
5ed58cbd
RS
2098
2099=item *
2100
2101All C header files from the top-level directory of the distribution are now
2102installed on VMS, providing consistency with a long-standing practice on other
2103platforms. Previously only a subset were installed, which broke non-core
2104extension builds for extensions that depended on the missing include files.
2105
2106=item *
2107
2108Quotes are now removed from the command verb (but not the parameters) for
2109commands spawned via C<system>, backticks, or a piped C<open>. Previously,
2110quotes on the verb were passed through to DCL, which would fail to recognize
2111the command. Also, if the verb is actually a path to an image or command
2112procedure on an ODS-5 volume, quoting it now allows the path to contain spaces.
2113
2114=item *
2115
2116The B<a2p> build has been fixed for the HP C++ compiler on OpenVMS.
2117
2118=back
2119
2120=head3 Win32
2121
2122=over
2123
2124=item *
2125
2126Perl can now be built using Microsoft's Visual C++ 2012 compiler by specifying
2127CCTYPE=MSVC110 (or MSVC110FREE if you are using the free Express edition for
2128Windows Desktop) in F<win32/Makefile>.
2129
2130=item *
2131
f105b7be 2132The option to build without C<USE_SOCKETS_AS_HANDLES> has been removed.
5ed58cbd
RS
2133
2134=item *
2135
2136Fixed a problem where perl could crash while cleaning up threads (including the
2137main thread) in threaded debugging builds on Win32 and possibly other platforms
2138[perl #114496].
2139
2140=item *
2141
2142A rare race condition that would lead to L<sleep|perlfunc/sleep> taking more
2143time than requested, and possibly even hanging, has been fixed [perl #33096].
2144
2145=item *
2146
2147C<link> on Win32 now attempts to set C<$!> to more appropriate values
2148based on the Win32 API error code. [perl #112272]
2149
2150Perl no longer mangles the environment block, e.g. when launching a new
2151sub-process, when the environment contains non-ASCII characters. Known
2152problems still remain, however, when the environment contains characters
2153outside of the current ANSI codepage (e.g. see the item about Unicode in
2154C<%ENV> in L<http://perl5.git.perl.org/perl.git/blob/HEAD:/Porting/todo.pod>).
2155[perl #113536]
2156
2157=item *
2158
2159Building perl with some Windows compilers used to fail due to a problem
2160with miniperl's C<glob> operator (which uses the C<perlglob> program)
2161deleting the PATH environment variable [perl #113798].
2162
2163=item *
2164
f105b7be 2165A new makefile option, C<USE_64_BIT_INT>, has been added to the Windows
5ed58cbd
RS
2166makefiles. Set this to "define" when building a 32-bit perl if you want
2167it to use 64-bit integers.
2168
2169Machine code size reductions, already made to the DLLs of XS modules in
e612b5a0 2170Perl v5.17.2, have now been extended to the perl DLL itself.
5ed58cbd 2171
e612b5a0 2172Building with VC++ 6.0 was inadvertently broken in Perl v5.17.2 but has
5ed58cbd
RS
2173now been fixed again.
2174
2175=back
2176
2177=head3 WinCE
2178
2179Building on WinCE is now possible once again, although more work is required
2180to fully restore a clean build.
2181
2182=head1 Internal Changes
2183
2184=over
2185
2186=item *
2187
4263dd11 2188Synonyms for the misleadingly named C<av_len()> have been created:
5ed58cbd
RS
2189C<av_top_index()> and C<av_tindex>. All three of these return the
2190number of the highest index in the array, not the number of elements it
2191contains.
2192
2193=item *
2194
2195SvUPGRADE() is no longer an expression. Originally this macro (and its
2196underlying function, sv_upgrade()) were documented as boolean, although
2197in reality they always croaked on error and never returned false. In 2005
2198the documentation was updated to specify a void return value, but
2199SvUPGRADE() was left always returning 1 for backwards compatibility. This
2200has now been removed, and SvUPGRADE() is now a statement with no return
2201value.
2202
2203So this is now a syntax error:
2204
2205 if (!SvUPGRADE(sv)) { croak(...); }
2206
2207If you have code like that, simply replace it with
2208
2209 SvUPGRADE(sv);
2210
237b9c6d 2211or to avoid compiler warnings with older perls, possibly
5ed58cbd
RS
2212
2213 (void)SvUPGRADE(sv);
2214
2215=item *
2216
2217Perl has a new copy-on-write mechanism that allows any SvPOK scalar to be
2218upgraded to a copy-on-write scalar. A reference count on the string buffer
d16360cf
RS
2219is stored in the string buffer itself. This feature is B<not enabled by
2220default>.
5ed58cbd 2221
d16360cf
RS
2222It can be enabled in a perl build by running F<Configure> with
2223B<-Accflags=-DPERL_NEW_COPY_ON_WRITE>, and we would encourage XS authors
2224to try their code with such an enabled perl, and provide feedback.
2225Unfortunately, there is not yet a good guide to updating XS code to cope
2226with COW. Until such a document is available, consult the perl5-porters
2227mailing list.
5ed58cbd 2228
d16360cf
RS
2229It breaks a few XS modules by allowing copy-on-write scalars to go
2230through code paths that never encountered them before.
5ed58cbd
RS
2231
2232=item *
2233
2234Copy-on-write no longer uses the SvFAKE and SvREADONLY flags. Hence,
2235SvREADONLY indicates a true read-only SV.
2236
2237Use the SvIsCOW macro (as before) to identify a copy-on-write scalar.
2238
2239=item *
2240
f105b7be 2241C<PL_glob_index> is gone.
5ed58cbd
RS
2242
2243=item *
2244
2245The private Perl_croak_no_modify has had its context parameter removed. It is
2246now has a void prototype. Users of the public API croak_no_modify remain
2247unaffected.
2248
2249=item *
2250
2251Copy-on-write (shared hash key) scalars are no longer marked read-only.
2252C<SvREADONLY> returns false on such an SV, but C<SvIsCOW> still returns
2253true.
2254
2255=item *
2256
2257A new op type, C<OP_PADRANGE> has been introduced. The perl peephole
2258optimiser will, where possible, substitute a single padrange op for a
2259pushmark followed by one or more pad ops, and possibly also skipping list
2260and nextstate ops. In addition, the op can carry out the tasks associated
f105b7be 2261with the RHS of a C<< my(...) = @_ >> assignment, so those ops may be optimised
5ed58cbd
RS
2262away too.
2263
2264=item *
2265
2266Case-insensitive matching inside a [bracketed] character class with a
2267multi-character fold no longer excludes one of the possibilities in the
2268circumstances that it used to. [perl #89774].
2269
2270=item *
2271
2272C<PL_formfeed> has been removed.
2273
2274=item *
2275
2276The regular expression engine no longer reads one byte past the end of the
2277target string. While for all internally well-formed scalars this should
2278never have been a problem, this change facilitates clever tricks with
2279string buffers in CPAN modules. [perl #73542]
2280
2281=item *
2282
2283Inside a BEGIN block, C<PL_compcv> now points to the currently-compiling
2284subroutine, rather than the BEGIN block itself.
2285
2286=item *
2287
2288C<mg_length> has been deprecated.
2289
2290=item *
2291
2292C<sv_len> now always returns a byte count and C<sv_len_utf8> a character
2293count. Previously, C<sv_len> and C<sv_len_utf8> were both buggy and would
2294sometimes returns bytes and sometimes characters. C<sv_len_utf8> no longer
be12dd22 2295assumes that its argument is in UTF-8. Neither of these creates UTF-8 caches
5ed58cbd
RS
2296for tied or overloaded values or for non-PVs any more.
2297
2298=item *
2299
2300C<sv_mortalcopy> now copies string buffers of shared hash key scalars when
2301called from XS modules [perl #79824].
2302
2303=item *
2304
2305C<RXf_SPLIT> and C<RXf_SKIPWHITE> are no longer used. They are now
2306#defined as 0.
2307
2308=item *
2309
2310The new C<RXf_MODIFIES_VARS> flag can be set by custom regular expression
2311engines to indicate that the execution of the regular expression may cause
2312variables to be modified. This lets C<s///> know to skip certain
2313optimisations. Perl's own regular expression engine sets this flag for the
2314special backtracking verbs that set $REGMARK and $REGERROR.
2315
2316=item *
2317
2318The APIs for accessing lexical pads have changed considerably.
2319
2320C<PADLIST>s are now longer C<AV>s, but their own type instead.
2321C<PADLIST>s now contain a C<PAD> and a C<PADNAMELIST> of C<PADNAME>s,
2322rather than C<AV>s for the pad and the list of pad names. C<PAD>s,
2323C<PADNAMELIST>s, and C<PADNAME>s are to be accessed as such through the
2324newly added pad API instead of the plain C<AV> and C<SV> APIs. See
2325L<perlapi> for details.
2326
2327=item *
2328
2329In the regex API, the numbered capture callbacks are passed an index
2330indicating what match variable is being accessed. There are special
2331index values for the C<$`, $&, $&> variables. Previously the same three
2332values were used to retrieve C<${^PREMATCH}, ${^MATCH}, ${^POSTMATCH}>
2333too, but these have now been assigned three separate values. See
2334L<perlreapi/Numbered capture callbacks>.
2335
2336=item *
2337
2338C<PL_sawampersand> was previously a boolean indicating that any of
2339C<$`, $&, $&> had been seen; it now contains three one-bit flags
2340indicating the presence of each of the variables individually.
2341
2342=item *
2343
2344The C<CV *> typemap entry now supports C<&{}> overloading and typeglobs,
2345just like C<&{...}> [perl #96872].
2346
2347=item *
2348
2349The C<SVf_AMAGIC> flag to indicate overloading is now on the stash, not the
2350object. It is now set automatically whenever a method or @ISA changes, so
2351its meaning has changed, too. It now means "potentially overloaded". When
2352the overload table is calculated, the flag is automatically turned off if
2353there is no overloading, so there should be no noticeable slowdown.
2354
2355The staleness of the overload tables is now checked when overload methods
2356are invoked, rather than during C<bless>.
2357
2358"A" magic is gone. The changes to the handling of the C<SVf_AMAGIC> flag
2359eliminate the need for it.
2360
2361C<PL_amagic_generation> has been removed as no longer necessary. For XS
2362modules, it is now a macro alias to C<PL_na>.
2363
2364The fallback overload setting is now stored in a stash entry separate from
2365overloadedness itself.
2366
2367=item *
2368
2369The character-processing code has been cleaned up in places. The changes
2370should be operationally invisible.
2371
2372=item *
2373
e612b5a0 2374The C<study> function was made a no-op in v5.16. It was simply disabled via
5ed58cbd
RS
2375a C<return> statement; the code was left in place. Now the code supporting
2376what C<study> used to do has been removed.
2377
2378=item *
2379
2380Under threaded perls, there is no longer a separate PV allocated for every
2381COP to store its package name (C<< cop->stashpv >>). Instead, there is an
2382offset (C<< cop->stashoff >>) into the new C<PL_stashpad> array, which
2383holds stash pointers.
2384
2385=item *
2386
2387In the pluggable regex API, the C<regexp_engine> struct has acquired a new
2388field C<op_comp>, which is currently just for perl's internal use, and
f105b7be 2389should be initialized to NULL by other regex plugin modules.
5ed58cbd
RS
2390
2391=item *
2392
7779650e 2393A new function C<alloccopstash> has been added to the API, but is considered
5ed58cbd
RS
2394experimental. See L<perlapi>.
2395
2396=item *
2397
2398Perl used to implement get magic in a way that would sometimes hide bugs in
4263dd11 2399code that could call mg_get() too many times on magical values. This hiding of
5ed58cbd
RS
2400errors no longer occurs, so long-standing bugs may become visible now. If
2401you see magic-related errors in XS code, check to make sure it, together
2402with the Perl API functions it uses, calls mg_get() only once on SvGMAGICAL()
2403values.
2404
2405=item *
2406
2407OP allocation for CVs now uses a slab allocator. This simplifies
2408memory management for OPs allocated to a CV, so cleaning up after a
2409compilation error is simpler and safer [perl #111462][perl #112312].
2410
2411=item *
2412
f105b7be 2413C<PERL_DEBUG_READONLY_OPS> has been rewritten to work with the new slab
5ed58cbd
RS
2414allocator, allowing it to catch more violations than before.
2415
2416=item *
2417
f105b7be
KE
2418The old slab allocator for ops, which was only enabled for C<PERL_IMPLICIT_SYS>
2419and C<PERL_DEBUG_READONLY_OPS>, has been retired.
5ed58cbd
RS
2420
2421=back
2422
2423=head1 Selected Bug Fixes
2424
2425=over 4
2426
2427=item *
2428
2429Here-doc terminators no longer require a terminating newline character when
2430they occur at the end of a file. This was already the case at the end of a
2431string eval [perl #65838].
2432
2433=item *
2434
f105b7be 2435C<-DPERL_GLOBAL_STRUCT> builds now free the global struct B<after>
5ed58cbd
RS
2436they've finished using it.
2437
2438=item *
2439
2440A trailing '/' on a path in @INC will no longer have an additional '/'
2441appended.
2442
2443=item *
2444
2445The C<:crlf> layer now works when unread data doesn't fit into its own
2446buffer. [perl #112244].
2447
2448=item *
2449
2450C<ungetc()> now handles UTF-8 encoded data. [perl #116322].
2451
2452=item *
2453
2454A bug in the core typemap caused any C types that map to the T_BOOL core
2455typemap entry to not be set, updated, or modified when the T_BOOL variable was
2456used in an OUTPUT: section with an exception for RETVAL. T_BOOL in an INPUT:
2457section was not affected. Using a T_BOOL return type for an XSUB (RETVAL)
2458was not affected. A side effect of fixing this bug is, if a T_BOOL is specified
2459in the OUTPUT: section (which previous did nothing to the SV), and a read only
2460SV (literal) is passed to the XSUB, croaks like "Modification of a read-only
2461value attempted" will happen. [perl #115796]
2462
2463=item *
2464
2465On many platforms, providing a directory name as the script name caused perl
2466to do nothing and report success. It should now universally report an error
2467and exit nonzero. [perl #61362]
2468
2469=item *
2470
2471C<sort {undef} ...> under fatal warnings no longer crashes. It had
e612b5a0 2472begun crashing in Perl v5.16.
5ed58cbd
RS
2473
2474=item *
2475
2476Stashes blessed into each other
2477(C<bless \%Foo::, 'Bar'; bless \%Bar::, 'Foo'>) no longer result in double
e612b5a0 2478frees. This bug started happening in Perl v5.16.
5ed58cbd
RS
2479
2480=item *
2481
2482Numerous memory leaks have been fixed, mostly involving fatal warnings and
2483syntax errors.
2484
2485=item *
2486
2487Some failed regular expression matches such as C<'f' =~ /../g> were not
2488resetting C<pos>. Also, "match-once" patterns (C<m?...?g>) failed to reset
2489it, too, when invoked a second time [perl #23180].
2490
2491=item *
2492
2493Accessing C<$&> after a pattern match now works if it had not been seen
2494before the match. I.e., this applies to C<${'&'}> (under C<no strict>) and
2495C<eval '$&'>. The same applies to C<$'> and C<$`> [perl #4289].
2496
2497=item *
2498
2499Several bugs involving C<local *ISA> and C<local *Foo::> causing stale
2500MRO caches have been fixed.
2501
2502=item *
2503
2504Defining a subroutine when its typeglob has been aliased no longer results
e612b5a0 2505in stale method caches. This bug was introduced in Perl v5.10.
5ed58cbd
RS
2506
2507=item *
2508
2509Localising a typeglob containing a subroutine when the typeglob's package
2510has been deleted from its parent stash no longer produces an error. This
e612b5a0 2511bug was introduced in Perl v5.14.
5ed58cbd
RS
2512
2513=item *
2514
2515Under some circumstances, C<local *method=...> would fail to reset method
2516caches upon scope exit.
2517
2518=item *
2519
2520C</[.foo.]/> is no longer an error, but produces a warning (as before) and
2521is treated as C</[.fo]/> [perl #115818].
2522
2523=item *
2524
2525C<goto $tied_var> now calls FETCH before deciding what type of goto
2526(subroutine or label) this is.
2527
2528=item *
2529
2530Renaming packages through glob assignment
2531(C<*Foo:: = *Bar::; *Bar:: = *Baz::>) in combination with C<m?...?> and
2532C<reset> no longer makes threaded builds crash.
2533
2534=item *
2535
2536A number of bugs related to assigning a list to hash have been fixed. Many of
2537these involve lists with repeated keys like C<(1, 1, 1, 1)>.
2538
2539=over 4
2540
2541=item *
2542
2543The expression C<scalar(%h = (1, 1, 1, 1))> now returns C<4>, not C<2>.
2544
2545=item *
2546
2547The return value of C<%h = (1, 1, 1)> in list context was wrong. Previously
2548this would return C<(1, undef, 1)>, now it returns C<(1, undef)>.
2549
2550=item *
2551
2552Perl now issues the same warning on C<($s, %h) = (1, {})> as it does for
2553C<(%h) = ({})>, "Reference found where even-sized list expected".
2554
2555=item *
2556
2557A number of additional edge cases in list assignment to hashes were
2558corrected. For more details see commit 23b7025ebc.
2559
2560=back
2561
2562=item *
2563
2564Attributes applied to lexical variables no longer leak memory.
2565[perl #114764]
2566
2567=item *
2568
2569C<dump>, C<goto>, C<last>, C<next>, C<redo> or C<require> followed by a
2570bareword (or version) and then an infix operator is no longer a syntax
2571error. It used to be for those infix operators (like C<+>) that have a
2572different meaning where a term is expected. [perl #105924]
2573
2574=item *
2575
2576C<require a::b . 1> and C<require a::b + 1> no longer produce erroneous
2577ambiguity warnings. [perl #107002]
2578
2579=item *
2580
2581Class method calls are now allowed on any string, and not just strings
2582beginning with an alphanumeric character. [perl #105922]
2583
2584=item *
2585
2586An empty pattern created with C<qr//> used in C<m///> no longer triggers
2587the "empty pattern reuses last pattern" behaviour. [perl #96230]
2588
2589=item *
2590
2591Tying a hash during iteration no longer results in a memory leak.
2592
2593=item *
2594
2595Freeing a tied hash during iteration no longer results in a memory leak.
2596
2597=item *
2598
2599List assignment to a tied array or hash that dies on STORE no longer
2600results in a memory leak.
2601
2602=item *
2603
2604If the hint hash (C<%^H>) is tied, compile-time scope entry (which copies
2605the hint hash) no longer leaks memory if FETCH dies. [perl #107000]
2606
2607=item *
2608
2609Constant folding no longer inappropriately triggers the special
2610C<split " "> behaviour. [perl #94490]
2611
2612=item *
2613
2614C<defined scalar(@array)>, C<defined do { &foo }>, and similar constructs
2615now treat the argument to C<defined> as a simple scalar. [perl #97466]
2616
2617=item *
2618
2619Running a custom debugging that defines no C<*DB::DB> glob or provides a
2620subroutine stub for C<&DB::DB> no longer results in a crash, but an error
2621instead. [perl #114990]
2622
2623=item *
2624
2625C<reset ""> now matches its documentation. C<reset> only resets C<m?...?>
2626patterns when called with no argument. An empty string for an argument now
2627does nothing. (It used to be treated as no argument.) [perl #97958]
2628
2629=item *
2630
2631C<printf> with an argument returning an empty list no longer reads past the
2632end of the stack, resulting in erratic behaviour. [perl #77094]
2633
2634=item *
2635
2636C<--subname> no longer produces erroneous ambiguity warnings.
2637[perl #77240]
2638
2639=item *
2640
2641C<v10> is now allowed as a label or package name. This was inadvertently
e612b5a0 2642broken when v-strings were added in Perl v5.6. [perl #56880]
5ed58cbd
RS
2643
2644=item *
2645
2646C<length>, C<pos>, C<substr> and C<sprintf> could be confused by ties,
2647overloading, references and typeglobs if the stringification of such
be12dd22 2648changed the internal representation to or from UTF-8. [perl #114410]
5ed58cbd
RS
2649
2650=item *
2651
2652utf8::encode now calls FETCH and STORE on tied variables. utf8::decode now
2653calls STORE (it was already calling FETCH).
2654
2655=item *
2656
2657C<$tied =~ s/$non_utf8/$utf8/> no longer loops infinitely if the tied
2658variable returns a Latin-1 string, shared hash key scalar, or reference or
2ae351f8 2659typeglob that stringifies as ASCII or Latin-1. This was a regression from
e612b5a0 2660v5.12.
5ed58cbd
RS
2661
2662=item *
2663
2664C<s///> without /e is now better at detecting when it needs to forego
2665certain optimisations, fixing some buggy cases:
2666
2667=over
2668
2669=item *
2670
2671Match variables in certain constructs (C<&&>, C<||>, C<..> and others) in
2672the replacement part; e.g., C<s/(.)/$l{$a||$1}/g>. [perl #26986]
2673
2674=item *
2675
2676Aliases to match variables in the replacement.
2677
2678=item *
2679
2680C<$REGERROR> or C<$REGMARK> in the replacement. [perl #49190]
2681
2682=item *
2683
2684An empty pattern (C<s//$foo/>) that causes the last-successful pattern to
2685be used, when that pattern contains code blocks that modify the variables
2686in the replacement.
2687
2688=back
2689
2690=item *
2691
2692The taintedness of the replacement string no longer affects the taintedness
2693of the return value of C<s///e>.
2694
2695=item *
2696
2697The C<$|> autoflush variable is created on-the-fly when needed. If this
2698happened (e.g., if it was mentioned in a module or eval) when the
2699currently-selected filehandle was a typeglob with an empty IO slot, it used
2700to crash. [perl #115206]
2701
2702=item *
2703
2704Line numbers at the end of a string eval are no longer off by one.
2705[perl #114658]
2706
2707=item *
2708
2709@INC filters (subroutines returned by subroutines in @INC) that set $_ to a
2710copy-on-write scalar no longer cause the parser to modify that string
2711buffer in place.
2712
2713=item *
2714
2715C<length($object)> no longer returns the undefined value if the object has
2716string overloading that returns undef. [perl #115260]
2717
2718=item *
2719
2720The use of C<PL_stashcache>, the stash name lookup cache for method calls, has
2721been restored,
2722
2723Commit da6b625f78f5f133 in August 2011 inadvertently broke the code that looks
2724up values in C<PL_stashcache>. As it's a only cache, quite correctly everything
2725carried on working without it.
2726
2727=item *
2728
e612b5a0 2729The error "Can't localize through a reference" had disappeared in v5.16.0
5ed58cbd 2730when C<local %$ref> appeared on the last line of an lvalue subroutine.
e612b5a0 2731This error disappeared for C<\local %$ref> in perl v5.8.1. It has now
5ed58cbd
RS
2732been restored.
2733
2734=item *
2735
2736The parsing of here-docs has been improved significantly, fixing several
2737parsing bugs and crashes and one memory leak, and correcting wrong
2738subsequent line numbers under certain conditions.
2739
2740=item *
2741
2742Inside an eval, the error message for an unterminated here-doc no longer
2743has a newline in the middle of it [perl #70836].
2744
2745=item *
2746
2747A substitution inside a substitution pattern (C<s/${s|||}//>) no longer
2748confuses the parser.
2749
2750=item *
2751
2752It may be an odd place to allow comments, but C<s//"" # hello/e> has
2753always worked, I<unless> there happens to be a null character before the
2754first #. Now it works even in the presence of nulls.
2755
2756=item *
2757
2758An invalid range in C<tr///> or C<y///> no longer results in a memory leak.
2759
2760=item *
2761
2762String eval no longer treats a semicolon-delimited quote-like operator at
2763the very end (C<eval 'q;;'>) as a syntax error.
2764
2765=item *
2766
2767C<< warn {$_ => 1} + 1 >> is no longer a syntax error. The parser used to
2768get confused with certain list operators followed by an anonymous hash and
2769then an infix operator that shares its form with a unary operator.
2770
2771=item *
2772
2773C<(caller $n)[6]> (which gives the text of the eval) used to return the
2774actual parser buffer. Modifying it could result in crashes. Now it always
2775returns a copy. The string returned no longer has "\n;" tacked on to the
2776end. The returned text also includes here-doc bodies, which used to be
2777omitted.
2778
2779=item *
2780
be12dd22
RS
2781Reset the UTF-8 position cache when accessing magical variables to avoid the
2782string buffer and the UTF-8 position cache getting out of sync
5ed58cbd
RS
2783[perl #114410].
2784
2785=item *
2786
be12dd22
RS
2787Various cases of get magic being called twice for magical UTF-8
2788strings have been fixed.
5ed58cbd
RS
2789
2790=item *
2791
2792This code (when not in the presence of C<$&> etc)
2793
2794 $_ = 'x' x 1_000_000;
2795 1 while /(.)/;
2796
2797used to skip the buffer copy for performance reasons, but suffered from C<$1>
2798etc changing if the original string changed. That's now been fixed.
2799
2800=item *
2801
2802Perl doesn't use PerlIO anymore to report out of memory messages, as PerlIO
2803might attempt to allocate more memory.
2804
2805=item *
2806
2807In a regular expression, if something is quantified with C<{n,m}> where
2808C<S<n E<gt> m>>, it can't possibly match. Previously this was a fatal
2809error, but now is merely a warning (and that something won't match).
2810[perl #82954].
2811
2812=item *
2813
2814It used to be possible for formats defined in subroutines that have
2815subsequently been undefined and redefined to close over variables in the
2816wrong pad (the newly-defined enclosing sub), resulting in crashes or
2817"Bizarre copy" errors.
2818
2819=item *
2820
2821Redefinition of XSUBs at run time could produce warnings with the wrong
2822line number.
2823
2824=item *
2825
2826The %vd sprintf format does not support version objects for alpha versions.
2827It used to output the format itself (%vd) when passed an alpha version, and
2828also emit an "Invalid conversion in printf" warning. It no longer does,
2829but produces the empty string in the output. It also no longer leaks
2830memory in this case.
2831
2832=item *
2833
2834C<< $obj->SUPER::method >> calls in the main package could fail if the
2835SUPER package had already been accessed by other means.
2836
2837=item *
2838
f105b7be 2839Stash aliasing (C<< *foo:: = *bar:: >>) no longer causes SUPER calls to ignore
5ed58cbd
RS
2840changes to methods or @ISA or use the wrong package.
2841
2842=item *
2843
2844Method calls on packages whose names end in ::SUPER are no longer treated
2845as SUPER method calls, resulting in failure to find the method.
2846Furthermore, defining subroutines in such packages no longer causes them to
2847be found by SUPER method calls on the containing package [perl #114924].
2848
2849=item *
2850
2851C<\w> now matches the code points U+200C (ZERO WIDTH NON-JOINER) and U+200D
2852(ZERO WIDTH JOINER). C<\W> no longer matches these. This change is because
2853Unicode corrected their definition of what C<\w> should match.
2854
2855=item *
2856
2857C<dump LABEL> no longer leaks its label.
2858
2859=item *
2860
2861Constant folding no longer changes the behaviour of functions like C<stat()>
2862and C<truncate()> that can take either filenames or handles.
2863C<stat 1 ? foo : bar> nows treats its argument as a file name (since it is an
2864arbitrary expression), rather than the handle "foo".
2865
2866=item *
2867
2868C<truncate FOO, $len> no longer falls back to treating "FOO" as a file name if
e612b5a0 2869the filehandle has been deleted. This was broken in Perl v5.16.0.
5ed58cbd
RS
2870
2871=item *
2872
2873Subroutine redefinitions after sub-to-glob and glob-to-glob assignments no
2874longer cause double frees or panic messages.
2875
2876=item *
2877
2878C<s///> now turns vstrings into plain strings when performing a substitution,
2879even if the resulting string is the same (C<s/a/a/>).
2880
2881=item *
2882
2883Prototype mismatch warnings no longer erroneously treat constant subs as having
2884no prototype when they actually have "".
2885
2886=item *
2887
2888Constant subroutines and forward declarations no longer prevent prototype
2889mismatch warnings from omitting the sub name.
2890
2891=item *
2892
2893C<undef> on a subroutine now clears call checkers.
2894
2895=item *
2896
e612b5a0 2897The C<ref> operator started leaking memory on blessed objects in Perl v5.16.0.
5ed58cbd
RS
2898This has been fixed [perl #114340].
2899
2900=item *
2901
2902C<use> no longer tries to parse its arguments as a statement, making
2903C<use constant { () };> a syntax error [perl #114222].
2904
2905=item *
2906
2907On debugging builds, "uninitialized" warnings inside formats no longer cause
2908assertion failures.
2909
2910=item *
2911
2912On debugging builds, subroutines nested inside formats no longer cause
2913assertion failures [perl #78550].
2914
2915=item *
2916
2917Formats and C<use> statements are now permitted inside formats.
2918
2919=item *
2920
2921C<print $x> and C<sub { print $x }-E<gt>()> now always produce the same output.
2922It was possible for the latter to refuse to close over $x if the variable was
2923not active; e.g., if it was defined outside a currently-running named
2924subroutine.
2925
2926=item *
2927
2928Similarly, C<print $x> and C<print eval '$x'> now produce the same output.
2929This also allows "my $x if 0" variables to be seen in the debugger [perl
2930#114018].
2931
2932=item *
2933
2934Formats called recursively no longer stomp on their own lexical variables, but
2935each recursive call has its own set of lexicals.
2936
2937=item *
2938
2939Attempting to free an active format or the handle associated with it no longer
2940results in a crash.
2941
2942=item *
2943
2944Format parsing no longer gets confused by braces, semicolons and low-precedence
2945operators. It used to be possible to use braces as format delimiters (instead
2946of C<=> and C<.>), but only sometimes. Semicolons and low-precedence operators
2947in format argument lines no longer confuse the parser into ignoring the line's
2948return value. In format argument lines, braces can now be used for anonymous
2949hashes, instead of being treated always as C<do> blocks.
2950
2951=item *
2952
2953Formats can now be nested inside code blocks in regular expressions and other
2954quoted constructs (C</(?{...})/> and C<qq/${...}/>) [perl #114040].
2955
2956=item *
2957
2958Formats are no longer created after compilation errors.
2959
2960=item *
2961
2962Under debugging builds, the B<-DA> command line option started crashing in Perl
e612b5a0 2963v5.16.0. It has been fixed [perl #114368].
5ed58cbd
RS
2964
2965=item *
2966
2967A potential deadlock scenario involving the premature termination of a pseudo-
2968forked child in a Windows build with ithreads enabled has been fixed. This
2969resolves the common problem of the F<t/op/fork.t> test hanging on Windows [perl
2970#88840].
2971
2972=item *
2973
5ed58cbd
RS
2974The code which generates errors from C<require()> could potentially read one or
2975two bytes before the start of the filename for filenames less than three bytes
2976long and ending C</\.p?\z/>. This has now been fixed. Note that it could
2977never have happened with module names given to C<use()> or C<require()> anyway.
2978
2979=item *
2980
2981The handling of pathnames of modules given to C<require()> has been made
2982thread-safe on VMS.
2983
2984=item *
2985
d85cd26b
RS
2986Non-blocking sockets have been fixed on VMS.
2987
2988=item *
2989
5ed58cbd
RS
2990A bug in the compilation of a C</(?{})/> expression which affected the TryCatch
2991test suite has been fixed [perl #114242].
2992
2993=item *
2994
2995Pod can now be nested in code inside a quoted construct outside of a string
2996eval. This used to work only within string evals [perl #114040].
2997
2998=item *
2999
3000C<goto ''> now looks for an empty label, producing the "goto must have
3001label" error message, instead of exiting the program [perl #111794].
3002
3003=item *
3004
3005C<goto "\0"> now dies with "Can't find label" instead of "goto must have
3006label".
3007
3008=item *
3009
3010The C function C<hv_store> used to result in crashes when used on C<%^H>
3011[perl #111000].
3012
3013=item *
3014
3015A call checker attached to a closure prototype via C<cv_set_call_checker>
3016is now copied to closures cloned from it. So C<cv_set_call_checker> now
3017works inside an attribute handler for a closure.
3018
3019=item *
3020
3021Writing to C<$^N> used to have no effect. Now it croaks with "Modification
3022of a read-only value" by default, but that can be overridden by a custom
3023regular expression engine, as with C<$1> [perl #112184].
3024
3025=item *
3026
3027C<undef> on a control character glob (C<undef *^H>) no longer emits an
3028erroneous warning about ambiguity [perl #112456].
3029
3030=item *
3031
3032For efficiency's sake, many operators and built-in functions return the
3033same scalar each time. Lvalue subroutines and subroutines in the CORE::
3034namespace were allowing this implementation detail to leak through.
3035C<print &CORE::uc("a"), &CORE::uc("b")> used to print "BB". The same thing
3036would happen with an lvalue subroutine returning the return value of C<uc>.
3037Now the value is copied in such cases.
3038
3039=item *
3040
3041C<method {}> syntax with an empty block or a block returning an empty list
3042used to crash or use some random value left on the stack as its invocant.
3043Now it produces an error.
3044
3045=item *
3046
3047C<vec> now works with extremely large offsets (E<gt>2 GB) [perl #111730].
3048
3049=item *
3050
3051Changes to overload settings now take effect immediately, as do changes to
3052inheritance that affect overloading. They used to take effect only after
3053C<bless>.
3054
3055Objects that were created before a class had any overloading used to remain
3056non-overloaded even if the class gained overloading through C<use overload>
3057or @ISA changes, and even after C<bless>. This has been fixed
3058[perl #112708].
3059
3060=item *
3061
3062Classes with overloading can now inherit fallback values.
3063
3064=item *
3065
3066Overloading was not respecting a fallback value of 0 if there were
3067overloaded objects on both sides of an assignment operator like C<+=>
3068[perl #111856].
3069
3070=item *
3071
3072C<pos> now croaks with hash and array arguments, instead of producing
3073erroneous warnings.
3074
3075=item *
3076
3077C<while(each %h)> now implies C<while(defined($_ = each %h))>, like
3078C<readline> and C<readdir>.
3079
3080=item *
3081
3082Subs in the CORE:: namespace no longer crash after C<undef *_> when called
3083with no argument list (C<&CORE::time> with no parentheses).
3084
3085=item *
3086
3087C<unpack> no longer produces the "'/' must follow a numeric type in unpack"
3088error when it is the data that are at fault [perl #60204].
3089
3090=item *
3091
3092C<join> and C<"@array"> now call FETCH only once on a tied C<$">
3093[perl #8931].
3094
3095=item *
3096
3097Some subroutine calls generated by compiling core ops affected by a
3098C<CORE::GLOBAL> override had op checking performed twice. The checking
3099is always idempotent for pure Perl code, but the double checking can
3100matter when custom call checkers are involved.
3101
3102=item *
3103
3104A race condition used to exist around fork that could cause a signal sent to
3105the parent to be handled by both parent and child. Signals are now blocked
3106briefly around fork to prevent this from happening [perl #82580].
3107
3108=item *
3109
3110The implementation of code blocks in regular expressions, such as C<(?{})>
3111and C<(??{})>, has been heavily reworked to eliminate a whole slew of bugs.
3112The main user-visible changes are:
3113
3114=over 4
3115
3116=item *
3117
3118Code blocks within patterns are now parsed in the same pass as the
3119surrounding code; in particular it is no longer necessary to have balanced
3120braces: this now works:
3121
3122 /(?{ $x='{' })/
3123
3124This means that this error message is no longer generated:
3125
3126 Sequence (?{...}) not terminated or not {}-balanced in regex
3127
3128but a new error may be seen:
3129
3130 Sequence (?{...}) not terminated with ')'
3131
3132In addition, literal code blocks within run-time patterns are only
3133compiled once, at perl compile-time:
3134
3135 for my $p (...) {
3136 # this 'FOO' block of code is compiled once,
3137 # at the same time as the surrounding 'for' loop
3138 /$p{(?{FOO;})/;
3139 }
3140
3141=item *
3142
3143Lexical variables are now sane as regards scope, recursion and closure
3144behavior. In particular, C</A(?{B})C/> behaves (from a closure viewpoint)
3145exactly like C</A/ && do { B } && /C/>, while C<qr/A(?{B})C/> is like
3146C<sub {/A/ && do { B } && /C/}>. So this code now works how you might
3147expect, creating three regexes that match 0, 1, and 2:
3148
3149 for my $i (0..2) {
3150 push @r, qr/^(??{$i})$/;
3151 }
3152 "1" =~ $r[1]; # matches
3153
3154=item *
3155
3156The C<use re 'eval'> pragma is now only required for code blocks defined
3157at runtime; in particular in the following, the text of the C<$r> pattern is
3158still interpolated into the new pattern and recompiled, but the individual
3159compiled code-blocks within C<$r> are reused rather than being recompiled,
3160and C<use re 'eval'> isn't needed any more:
3161
3162 my $r = qr/abc(?{....})def/;
3163 /xyz$r/;
3164
3165=item *
3166
3167Flow control operators no longer crash. Each code block runs in a new
3168dynamic scope, so C<next> etc. will not see
3169any enclosing loops. C<return> returns a value
3170from the code block, not from any enclosing subroutine.
3171
3172=item *
3173
3174Perl normally caches the compilation of run-time patterns, and doesn't
3175recompile if the pattern hasn't changed, but this is now disabled if
3176required for the correct behavior of closures. For example:
3177
3178 my $code = '(??{$x})';
3179 for my $x (1..3) {
3180 # recompile to see fresh value of $x each time
3181 $x =~ /$code/;
3182 }
3183
3184=item *
3185
3186The C</msix> and C<(?msix)> etc. flags are now propagated into the return
3187value from C<(??{})>; this now works:
3188
3189 "AB" =~ /a(??{'b'})/i;
3190
3191=item *
3192
3193Warnings and errors will appear to come from the surrounding code (or for
3194run-time code blocks, from an eval) rather than from an C<re_eval>:
3195
3196 use re 'eval'; $c = '(?{ warn "foo" })'; /$c/;
3197 /(?{ warn "foo" })/;
3198
3199formerly gave:
3200
3201 foo at (re_eval 1) line 1.
3202 foo at (re_eval 2) line 1.
3203
3204and now gives:
3205
3206 foo at (eval 1) line 1.
3207 foo at /some/prog line 2.
3208
3209=back
3210
3211=item *
3212
2e7bc647
KW
3213Perl now can be recompiled to use any Unicode version. In v5.16, it
3214worked on Unicodes 6.0 and 6.1, but there were various bugs if earlier
3215releases were used; the older the release the more problems.
5ed58cbd
RS
3216
3217=item *
3218
3219C<vec> no longer produces "uninitialized" warnings in lvalue context
3220[perl #9423].
3221
3222=item *
3223
3224An optimization involving fixed strings in regular expressions could cause
3225a severe performance penalty in edge cases. This has been fixed
3226[perl #76546].
3227
3228=item *
3229
3230In certain cases, including empty subpatterns within a regular expression (such
3231as C<(?:)> or C<(?:|)>) could disable some optimizations. This has been fixed.
3232
3233=item *
3234
3235The "Can't find an opnumber" message that C<prototype> produces when passed
3236a string like "CORE::nonexistent_keyword" now passes UTF-8 and embedded
3237NULs through unchanged [perl #97478].
3238
3239=item *
3240
3241C<prototype> now treats magical variables like C<$1> the same way as
3242non-magical variables when checking for the CORE:: prefix, instead of
3243treating them as subroutine names.
3244
3245=item *
3246
3247Under threaded perls, a runtime code block in a regular expression could
3248corrupt the package name stored in the op tree, resulting in bad reads
3249in C<caller>, and possibly crashes [perl #113060].
3250
3251=item *
3252
3253Referencing a closure prototype (C<\&{$_[1]}> in an attribute handler for a
3254closure) no longer results in a copy of the subroutine (or assertion
3255failures on debugging builds).
3256
3257=item *
3258
3259C<eval '__PACKAGE__'> now returns the right answer on threaded builds if
3260the current package has been assigned over (as in
3261C<*ThisPackage:: = *ThatPackage::>) [perl #78742].
3262
3263=item *
3264
3265If a package is deleted by code that it calls, it is possible for C<caller>
3266to see a stack frame belonging to that deleted package. C<caller> could
3267crash if the stash's memory address was reused for a scalar and a
3268substitution was performed on the same scalar [perl #113486].
3269
3270=item *
3271
3272C<UNIVERSAL::can> no longer treats its first argument differently
3273depending on whether it is a string or number internally.
3274
3275=item *
3276
3277C<open> with C<< <& >> for the mode checks to see whether the third argument is
3278a number, in determining whether to treat it as a file descriptor or a handle
3279name. Magical variables like C<$1> were always failing the numeric check and
3280being treated as handle names.
3281
3282=item *
3283
3284C<warn>'s handling of magical variables (C<$1>, ties) has undergone several
3285fixes. C<FETCH> is only called once now on a tied argument or a tied C<$@>
3286[perl #97480]. Tied variables returning objects that stringify as "" are
3287no longer ignored. A tied C<$@> that happened to return a reference the
3288I<previous> time it was used is no longer ignored.
3289
3290=item *
3291
3292C<warn ""> now treats C<$@> with a number in it the same way, regardless of
3293whether it happened via C<$@=3> or C<$@="3">. It used to ignore the
3294former. Now it appends "\t...caught", as it has always done with
3295C<$@="3">.
3296
3297=item *
3298
3299Numeric operators on magical variables (e.g., S<C<$1 + 1>>) used to use
3300floating point operations even where integer operations were more appropriate,
3301resulting in loss of accuracy on 64-bit platforms [perl #109542].
3302
3303=item *
3304
3305Unary negation no longer treats a string as a number if the string happened
3306to be used as a number at some point. So, if C<$x> contains the string "dogs",
3307C<-$x> returns "-dogs" even if C<$y=0+$x> has happened at some point.
3308
3309=item *
3310
e612b5a0 3311In Perl v5.14, C<-'-10'> was fixed to return "10", not "+10". But magical
5ed58cbd
RS
3312variables (C<$1>, ties) were not fixed till now [perl #57706].
3313
3314=item *
3315
3316Unary negation now treats strings consistently, regardless of the internal
3317C<UTF8> flag.
3318
3319=item *
3320
3321A regression introduced in Perl v5.16.0 involving
3322C<tr/I<SEARCHLIST>/I<REPLACEMENTLIST>/> has been fixed. Only the first
3323instance is supposed to be meaningful if a character appears more than
3324once in C<I<SEARCHLIST>>. Under some circumstances, the final instance
3325was overriding all earlier ones. [perl #113584]
3326
3327=item *
3328
3329Regular expressions like C<qr/\87/> previously silently inserted a NUL
3330character, thus matching as if it had been written C<qr/\00087/>. Now it
3331matches as if it had been written as C<qr/87/>, with a message that the
3332sequence C<"\8"> is unrecognized.
3333
3334=item *
3335
3336C<__SUB__> now works in special blocks (C<BEGIN>, C<END>, etc.).
3337
3338=item *
3339
3340Thread creation on Windows could theoretically result in a crash if done
3341inside a C<BEGIN> block. It still does not work properly, but it no longer
3342crashes [perl #111610].
3343
3344=item *
3345
3346C<\&{''}> (with the empty string) now autovivifies a stub like any other
3347sub name, and no longer produces the "Unable to create sub" error
3348[perl #94476].
3349
3350=item *
3351
3352A regression introduced in v5.14.0 has been fixed, in which some calls
3353to the C<re> module would clobber C<$_> [perl #113750].
3354
3355=item *
3356
3357C<do FILE> now always either sets or clears C<$@>, even when the file can't be
3358read. This ensures that testing C<$@> first (as recommended by the
3359documentation) always returns the correct result.
3360
3361=item *
3362
3363The array iterator used for the C<each @array> construct is now correctly
237b9c6d
SK
3364reset when C<@array> is cleared [perl #75596]. This happens, for example, when
3365the array is globally assigned to, as in C<@array = (...)>, but not when its
5ed58cbd
RS
3366B<values> are assigned to. In terms of the XS API, it means that C<av_clear()>
3367will now reset the iterator.
3368
3369This mirrors the behaviour of the hash iterator when the hash is cleared.
3370
3371=item *
3372
3373C<< $class->can >>, C<< $class->isa >>, and C<< $class->DOES >> now return
3374correct results, regardless of whether that package referred to by C<$class>
3375exists [perl #47113].
3376
3377=item *
3378
3379Arriving signals no longer clear C<$@> [perl #45173].
3380
3381=item *
3382
3383Allow C<my ()> declarations with an empty variable list [perl #113554].
3384
3385=item *
3386
3387During parsing, subs declared after errors no longer leave stubs
3388[perl #113712].
3389
3390=item *
3391
3392Closures containing no string evals no longer hang on to their containing
3393subroutines, allowing variables closed over by outer subroutines to be
3394freed when the outer sub is freed, even if the inner sub still exists
3395[perl #89544].
3396
3397=item *
3398
3399Duplication of in-memory filehandles by opening with a "<&=" or ">&=" mode
e612b5a0 3400stopped working properly in v5.16.0. It was causing the new handle to
5ed58cbd
RS
3401reference a different scalar variable. This has been fixed [perl #113764].
3402
3403=item *
3404
3405C<qr//> expressions no longer crash with custom regular expression engines
3406that do not set C<offs> at regular expression compilation time
3407[perl #112962].
3408
3409=item *
3410
3411C<delete local> no longer crashes with certain magical arrays and hashes
3412[perl #112966].
3413
3414=item *
3415
3416C<local> on elements of certain magical arrays and hashes used not to
3417arrange to have the element deleted on scope exit, even if the element did
3418not exist before C<local>.
3419
3420=item *
3421
3422C<scalar(write)> no longer returns multiple items [perl #73690].
3423
3424=item *
3425
3426String to floating point conversions no longer misparse certain strings under
3427C<use locale> [perl #109318].
3428
3429=item *
3430
3431C<@INC> filters that die no longer leak memory [perl #92252].
3432
3433=item *
3434
3435The implementations of overloaded operations are now called in the correct
3436context. This allows, among other things, being able to properly override
3437C<< <> >> [perl #47119].
3438
3439=item *
3440
3441Specifying only the C<fallback> key when calling C<use overload> now behaves
3442properly [perl #113010].
3443
3444=item *
3445
3446C<< sub foo { my $a = 0; while ($a) { ... } } >> and
3447C<< sub foo { while (0) { ... } } >> now return the same thing [perl #73618].
3448
3449=item *
3450
3451String negation now behaves the same under C<use integer;> as it does
3452without [perl #113012].
3453
3454=item *
3455
3456C<chr> now returns the Unicode replacement character (U+FFFD) for -1,
3457regardless of the internal representation. -1 used to wrap if the argument
3458was tied or a string internally.
3459
3460=item *
3461
3462Using a C<format> after its enclosing sub was freed could crash as of
e612b5a0 3463perl v5.12.0, if the format referenced lexical variables from the outer sub.
5ed58cbd
RS
3464
3465=item *
3466
3467Using a C<format> after its enclosing sub was undefined could crash as of
e612b5a0 3468perl v5.10.0, if the format referenced lexical variables from the outer sub.
5ed58cbd
RS
3469
3470=item *
3471
3472Using a C<format> defined inside a closure, which format references
3473lexical variables from outside, never really worked unless the C<write>
e612b5a0 3474call was directly inside the closure. In v5.10.0 it even started crashing.
5ed58cbd
RS
3475Now the copy of that closure nearest the top of the call stack is used to
3476find those variables.
3477
3478=item *
3479
3480Formats that close over variables in special blocks no longer crash if a
3481stub exists with the same name as the special block before the special
3482block is compiled.
3483
3484=item *
3485
3486The parser no longer gets confused, treating C<eval foo ()> as a syntax
3487error if preceded by C<print;> [perl #16249].
3488
3489=item *
3490
3491The return value of C<syscall> is no longer truncated on 64-bit platforms
3492[perl #113980].
3493
3494=item *
3495
3496Constant folding no longer causes C<print 1 ? FOO : BAR> to print to the
3497FOO handle [perl #78064].
3498
3499=item *
3500
3501C<do subname> now calls the named subroutine and uses the file name it
3502returns, instead of opening a file named "subname".
3503
3504=item *
3505
3506Subroutines looked up by rv2cv check hooks (registered by XS modules) are
3507now taken into consideration when determining whether C<foo bar> should be
3508the sub call C<foo(bar)> or the method call C<< "bar"->foo >>.
3509
3510=item *
3511
3512C<CORE::foo::bar> is no longer treated specially, allowing global overrides
3513to be called directly via C<CORE::GLOBAL::uc(...)> [perl #113016].
3514
3515=item *
3516
3517Calling an undefined sub whose typeglob has been undefined now produces the
3518customary "Undefined subroutine called" error, instead of "Not a CODE
3519reference".
3520
3521=item *
3522
3523Two bugs involving @ISA have been fixed. C<*ISA = *glob_without_array> and
3524C<undef *ISA; @{*ISA}> would prevent future modifications to @ISA from
3525updating the internal caches used to look up methods. The
e612b5a0 3526*glob_without_array case was a regression from Perl v5.12.
5ed58cbd
RS
3527
3528=item *
3529
3530Regular expression optimisations sometimes caused C<$> with C</m> to
3531produce failed or incorrect matches [perl #114068].
3532
3533=item *
3534
3535C<__SUB__> now works in a C<sort> block when the enclosing subroutine is
3536predeclared with C<sub foo;> syntax [perl #113710].
3537
3538=item *
3539
3540Unicode properties only apply to Unicode code points, which leads to
3541some subtleties when regular expressions are matched against
3542above-Unicode code points. There is a warning generated to draw your
3543attention to this. However, this warning was being generated
3544inappropriately in some cases, such as when a program was being parsed.
3545Non-Unicode matches such as C<\w> and C<[:word;]> should not generate the
3546warning, as their definitions don't limit them to apply to only Unicode
3547code points. Now the message is only generated when matching against
3548C<\p{}> and C<\P{}>. There remains a bug, [perl #114148], for the very
3549few properties in Unicode that match just a single code point. The
3550warning is not generated if they are matched against an above-Unicode
3551code point.
3552
3553=item *
3554
3555Uninitialized warnings mentioning hash elements would only mention the
3556element name if it was not in the first bucket of the hash, due to an
3557off-by-one error.
3558
3559=item *
3560
3561A regular expression optimizer bug could cause multiline "^" to behave
3562incorrectly in the presence of line breaks, such that
3563C<"/\n\n" =~ m#\A(?:^/$)#im> would not match [perl #115242].
3564
3565=item *
3566
3567Failed C<fork> in list context no longer corrupts the stack.
3568C<@a = (1, 2, fork, 3)> used to gobble up the 2 and assign C<(1, undef, 3)>
3569if the C<fork> call failed.
3570
3571=item *
3572
3573Numerous memory leaks have been fixed, mostly involving tied variables that
3574die, regular expression character classes and code blocks, and syntax
3575errors.
3576
3577=item *
3578
3579Assigning a regular expression (C<${qr//}>) to a variable that happens to
3580hold a floating point number no longer causes assertion failures on
3581debugging builds.
3582
3583=item *
3584
3585Assigning a regular expression to a scalar containing a number no longer
f105b7be 3586causes subsequent numification to produce random numbers.
5ed58cbd
RS
3587
3588=item *
3589
3590Assigning a regular expression to a magic variable no longer wipes away the
e612b5a0 3591magic. This was a regression from v5.10.
5ed58cbd
RS
3592
3593=item *
3594
3595Assigning a regular expression to a blessed scalar no longer results in
e612b5a0 3596crashes. This was also a regression from v5.10.
5ed58cbd
RS
3597
3598=item *
3599
3600Regular expression can now be assigned to tied hash and array elements with
3601flattening into strings.
3602
3603=item *
3604
f105b7be 3605Numifying a regular expression no longer results in an uninitialized
5ed58cbd
RS
3606warning.
3607
3608=item *
3609
3610Negative array indices no longer cause EXISTS methods of tied variables to
e612b5a0 3611be ignored. This was a regression from v5.12.
5ed58cbd
RS
3612
3613=item *
3614
3615Negative array indices no longer result in crashes on arrays tied to
3616non-objects.
3617
3618=item *
3619
be12dd22
RS
3620C<$byte_overload .= $utf8> no longer results in doubly-encoded UTF-8 if the
3621left-hand scalar happened to have produced a UTF-8 string the last time
5ed58cbd
RS
3622overloading was invoked.
3623
3624=item *
3625
3626C<goto &sub> now uses the current value of @_, instead of using the array
3627the subroutine was originally called with. This means
3628C<local @_ = (...); goto &sub> now works [perl #43077].
3629
3630=item *
3631
3632If a debugger is invoked recursively, it no longer stomps on its own
3633lexical variables. Formerly under recursion all calls would share the same
3634set of lexical variables [perl #115742].
3635
3636=item *
3637
3638C<*_{ARRAY}> returned from a subroutine no longer spontaneously
3639becomes empty.
3640
3641=back
3642
3643=head1 Known Problems
3644
3645=over 4
3646
3647=item *
3648
7f50b25b 3649There are no known regressions. Please report any bugs you find!
5ed58cbd
RS
3650
3651=back
3652
32b79602
RS
3653=head1 Obituary
3654
3655Hojung Yoon (AMORETTE), 24, of Seoul, South Korea, went to his long rest
3656on May 8, 2013 with llama figurine and autographed TIMTOADY card. He
3657was a brilliant young Perl 5 & 6 hacker and a devoted member of
55c6e7a8 3658Seoul.pm. He programmed Perl, talked Perl, ate Perl, and loved Perl. We
32b79602
RS
3659believe that he is still programming in Perl with his broken IBM laptop
3660somewhere. He will be missed.
3661
5ed58cbd 3662=head1 Acknowledgements
a75569c0 3663
dd38235c
RS
3664Perl v5.18.0 represents approximately 12 months of development since
3665Perl v5.16.0 and contains approximately 400,000 lines of changes across
36662,100 files from 113 authors.
3667
3668Perl continues to flourish into its third decade thanks to a vibrant
3669community of users and developers. The following people are known to
3670have contributed the improvements that became Perl v5.18.0:
3671
3672Aaron Crane, Aaron Trevena, Abhijit Menon-Sen, Adrian M. Enache, Alan
3673Haggai Alavi, Alexandr Ciornii, Andrew Tam, Andy Dougherty, Anton Nikishaev,
3674Aristotle Pagaltzis, Augustina Blair, Bob Ernst, Brad Gilbert, Breno G. de
3675Oliveira, Brian Carlson, Brian Fraser, Charlie Gonzalez, Chip Salzenberg, Chris
3676'BinGOs' Williams, Christian Hansen, Colin Kuskie, Craig A. Berry, Dagfinn
3677Ilmari Mannsåker, Daniel Dragan, Daniel Perrett, Darin McBride, Dave Rolsky,
3678David Golden, David Leadbeater, David Mitchell, David Nicol, Dominic
3679Hargreaves, E. Choroba, Eric Brine, Evan Miller, Father Chrysostomos, Florian
3680Ragwitz, François Perrad, George Greer, Goro Fuji, H.Merijn Brand, Herbert
3681Breunung, Hugo van der Sanden, Igor Zaytsev, James E Keenan, Jan Dubois,
3682Jasmine Ahuja, Jerry D. Hedden, Jess Robinson, Jesse Luehrs, Joaquin Ferrero,
3683Joel Berger, John Goodyear, John Peacock, Karen Etheridge, Karl Williamson,
3684Karthik Rajagopalan, Kent Fredric, Leon Timmermans, Lucas Holt, Lukas Mai,
3685Marcus Holland-Moritz, Markus Jansen, Martin Hasch, Matthew Horsfall, Max
3686Maischein, Michael G Schwern, Michael Schroeder, Moritz Lenz, Nicholas Clark,
3687Niko Tyni, Oleg Nesterov, Patrik Hägglund, Paul Green, Paul Johnson, Paul
3688Marquess, Peter Martini, Rafael Garcia-Suarez, Reini Urban, Renee Baecker,
3689Rhesa Rozendaal, Ricardo Signes, Robin Barker, Ronald J. Kimball, Ruslan
3690Zakirov, Salvador Fandiño, Sawyer X, Scott Lanning, Sergey Alekseev, Shawn M
3691Moore, Shirakata Kentaro, Shlomi Fish, Sisyphus, Smylers, Steffen Müller,
3692Steve Hay, Steve Peters, Steven Schubiger, Sullivan Beck, Sven Strickroth,
3693Sébastien Aperghis-Tramoni, Thomas Sibley, Tobias Leich, Tom Wyant, Tony Cook,
3694Vadim Konovalov, Vincent Pit, Volker Schatz, Walt Mankowski, Yves Orton,
3695Zefram.
3696
3697The list above is almost certainly incomplete as it is automatically generated
3698from version control history. In particular, it does not include the names of
3699the (very much appreciated) contributors who reported issues to the Perl bug
3700tracker.
3701
3702Many of the changes included in this version originated in the CPAN modules
3703included in Perl's core. We're grateful to the entire CPAN community for
3704helping Perl to flourish.
3705
3706For a more complete list of all of Perl's historical contributors, please see
3707the F<AUTHORS> file in the Perl source distribution.
f5b73711 3708
44691e6f
AB
3709=head1 Reporting Bugs
3710
e08634c5
SH
3711If you find what you think is a bug, you might check the articles recently
3712posted to the comp.lang.perl.misc newsgroup and the perl bug database at
3713http://rt.perl.org/perlbug/ . There may also be information at
3714http://www.perl.org/ , the Perl Home Page.
44691e6f 3715
e08634c5
SH
3716If you believe you have an unreported bug, please run the L<perlbug> program
3717included with your release. Be sure to trim your bug down to a tiny but
3718sufficient test case. Your bug report, along with the output of C<perl -V>,
3719will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
44691e6f
AB
3720
3721If the bug you are reporting has security implications, which make it
e08634c5
SH
3722inappropriate to send to a publicly archived mailing list, then please send it
3723to perl5-security-report@perl.org. This points to a closed subscription
3724unarchived mailing list, which includes all the core committers, who will be
3725able to help assess the impact of issues, figure out a resolution, and help
f9001595 3726co-ordinate the release of patches to mitigate or fix the problem across all
e08634c5
SH
3727platforms on which Perl is supported. Please only use this address for
3728security issues in the Perl core, not for modules independently distributed on
3729CPAN.
44691e6f
AB
3730
3731=head1 SEE ALSO
3732
e08634c5
SH
3733The F<Changes> file for an explanation of how to view exhaustive details on
3734what changed.
44691e6f
AB
3735
3736The F<INSTALL> file for how to build Perl.
3737
3738The F<README> file for general stuff.
3739
3740The F<Artistic> and F<Copying> files for copyright information.
3741
3742=cut