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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
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95exceed that of an integer. (SipHash uses a 16 byte seed).
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
124which might exceed that of an integer. (SipHash uses a 16 byte seed).
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
KE
631
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
5ed58cbd 637and
f105b7be
KE
638
639 U+2029 PARAGRAPH SEPARATOR.
5ed58cbd
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640
641=head2 User-defined charnames with surprising whitespace
642
643A user-defined character name with trailing or multiple spaces in a row is
644likely a typo. This now generates a warning when defined, on the assumption
645that uses of it will be unlikely to include the excess whitespace.
646
647=head2 Various XS-callable functions are now deprecated
648
649All the functions used to classify characters will be removed from a
650future version of Perl, and should not be used. With participating C
651compilers (e.g., gcc), compiling any file that uses any of these will
652generate a warning. These were not intended for public use; there are
653equivalent, faster, macros for most of them.
e612b5a0 654
2e7bc647 655See L<perlapi/Character classes>. The complete list is:
e612b5a0 656
5ed58cbd
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657C<is_uni_alnum>, C<is_uni_alnumc>, C<is_uni_alnumc_lc>,
658C<is_uni_alnum_lc>, C<is_uni_alpha>, C<is_uni_alpha_lc>,
659C<is_uni_ascii>, C<is_uni_ascii_lc>, C<is_uni_blank>,
660C<is_uni_blank_lc>, C<is_uni_cntrl>, C<is_uni_cntrl_lc>,
661C<is_uni_digit>, C<is_uni_digit_lc>, C<is_uni_graph>,
662C<is_uni_graph_lc>, C<is_uni_idfirst>, C<is_uni_idfirst_lc>,
663C<is_uni_lower>, C<is_uni_lower_lc>, C<is_uni_print>,
664C<is_uni_print_lc>, C<is_uni_punct>, C<is_uni_punct_lc>,
665C<is_uni_space>, C<is_uni_space_lc>, C<is_uni_upper>,
666C<is_uni_upper_lc>, C<is_uni_xdigit>, C<is_uni_xdigit_lc>,
667C<is_utf8_alnum>, C<is_utf8_alnumc>, C<is_utf8_alpha>,
668C<is_utf8_ascii>, C<is_utf8_blank>, C<is_utf8_char>,
669C<is_utf8_cntrl>, C<is_utf8_digit>, C<is_utf8_graph>,
670C<is_utf8_idcont>, C<is_utf8_idfirst>, C<is_utf8_lower>,
671C<is_utf8_mark>, C<is_utf8_perl_space>, C<is_utf8_perl_word>,
672C<is_utf8_posix_digit>, C<is_utf8_print>, C<is_utf8_punct>,
673C<is_utf8_space>, C<is_utf8_upper>, C<is_utf8_xdigit>,
674C<is_utf8_xidcont>, C<is_utf8_xidfirst>.
675
676In addition these three functions that have never worked properly are
677deprecated:
678C<to_uni_lower_lc>, C<to_uni_title_lc>, and C<to_uni_upper_lc>.
679
f105b7be 680=head2 Certain rare uses of backslashes within regexes are now deprecated
5ed58cbd
RS
681
682There are three pairs of characters that Perl recognizes as
683metacharacters in regular expression patterns: C<{}>, C<[]>, and C<()>.
684These can be used as well to delimit patterns, as in:
685
686 m{foo}
687 s(foo)(bar)
688
689Since they are metacharacters, they have special meaning to regular
690expression patterns, and it turns out that you can't turn off that
691special meaning by the normal means of preceding them with a backslash,
f105b7be 692if you use them, paired, within a pattern delimited by them. For
5ed58cbd
RS
693example, in
694
695 m{foo\{1,3\}}
696
697the backslashes do not change the behavior, and this matches
698S<C<"f o">> followed by one to three more occurrences of C<"o">.
699
700Usages like this, where they are interpreted as metacharacters, are
701exceedingly rare; we think there are none, for example, in all of CPAN.
702Hence, this deprecation should affect very little code. It does give
703notice, however, that any such code needs to change, which will in turn
704allow us to change the behavior in future Perl versions so that the
705backslashes do have an effect, and without fear that we are silently
706breaking any existing code.
707
d5f315e8
KW
708=head2 Splitting the tokens C<(?> and C<(*> in regular expressions
709
710A deprecation warning is now raised if the C<(> and C<?> are separated
711by white space or comments in C<(?...)> regular expression constructs.
712Similarly, if the C<(> and C<*> are separated in C<(*VERB...)>
713constructs.
714
e0a1dec5
LT
715=head2 Pre-PerlIO IO implementations
716
717Perl supports being built without PerlIO proper, using a stdio or sfio
718wrapper instead. A perl build like this will not support IO layers and
719thus Unicode IO, making it rather handicapped.
720
721PerlIO supports a C<stdio> layer if stdio use is desired, and similarly a
722sfio layer could be produced.
723
5ed58cbd
RS
724=head1 Future Deprecations
725
726=over
71e6aba6
RS
727
728=item *
729
4263dd11 730Platforms without support infrastructure
5ed58cbd
RS
731
732Both Windows CE and z/OS have been historically under-maintained, and are
733currently neither successfully building nor regularly being smoke tested.
734Efforts are underway to change this situation, but it should not be taken for
735granted that the platforms are safe and supported. If they do not become
736buildable and regularly smoked, support for them may be actively removed in
737future releases. If you have an interest in these platforms and you can lend
738your time, expertise, or hardware to help support these platforms, please let
739the perl development effort know by emailing C<perl5-porters@perl.org>.
740
741Some platforms that appear otherwise entirely dead are also on the short list
e612b5a0 742for removal between now and v5.20.0:
5ed58cbd
RS
743
744=over
745
746=item DG/UX
747
748=item NeXT
749
750=back
1993add8 751
ec985017
RS
752We also think it likely that current versions of Perl will no longer
753build AmigaOS, DJGPP, NetWare (natively), OS/2 and Plan 9. If you
754are using Perl on such a platform and have an interest in ensuring
755Perl's future on them, please contact us.
756
757We believe that Perl has long been unable to build on mixed endian
758architectures (such as PDP-11s), and intend to remove any remain
759support code. Similarly, code supporting the long umaintained GNU
760dld will be removed soon if no-one makes themselves known as an
761active user.
762
1993add8
RS
763=item *
764
5ed58cbd
RS
765Swapping of $< and $>
766
767For more information about this future deprecation, see L<the relevant RT
768ticket|https://rt.perl.org/rt3/Ticket/Display.html?id=96212>.
71e6aba6
RS
769
770=item *
771
5ed58cbd 772C<microperl>, long broken and of unclear present purpose, will be removed.
71e6aba6
RS
773
774=item *
775
5ed58cbd
RS
776Revamping C<< "\Q" >> semantics in double-quotish strings when combined with
777other escapes.
778
779There are several bugs and inconsistencies involving combinations
780of C<\Q> and escapes like C<\x>, C<\L>, etc., within a C<\Q...\E> pair.
781These need to be fixed, and doing so will necessarily change current
782behavior. The changes have not yet been settled.
71e6aba6 783
d5f315e8
KW
784=item *
785
786Use of C<$^>, where C<^> stands for any actual (non-printing) C0 control
787character will be disallowed in a future Perl version. Use C<${^}>
788instead (where again C<^> stands for a control character),
789or better, C<$^A> , where C<^> this time is a caret (CIRCUMFLEX ACCENT),
790and C<A> stands for any of the characters listed at the end of
791L<perlebcdic/OPERATOR DIFFERENCES>.
792
337fb649 793=back
2426c394 794
5ed58cbd
RS
795=head1 Performance Enhancements
796
797=over 4
2426c394 798
5ed58cbd 799=item *
2426c394 800
5ed58cbd
RS
801Lists of lexical variable declarations (C<my($x, $y)>) are now optimised
802down to a single op and are hence faster than before.
2426c394 803
5ed58cbd 804=item *
2426c394 805
5ed58cbd
RS
806A new C preprocessor define C<NO_TAINT_SUPPORT> was added that, if set,
807disables Perl's taint support altogether. Using the -T or -t command
808line flags will cause a fatal error. Beware that both core tests as
809well as many a CPAN distribution's tests will fail with this change. On
810the upside, it provides a small performance benefit due to reduced
811branching.
2426c394 812
5ed58cbd
RS
813B<Do not enable this unless you know exactly what you are getting yourself
814into.>
815
816=item *
817
818C<pack> with constant arguments is now constant folded in most cases
819[perl #113470].
820
821=item *
822
823Speed up in regular expression matching against Unicode properties. The
824largest gain is for C<\X>, the Unicode "extended grapheme cluster." The
825gain for it is about 35% - 40%. Bracketed character classes, e.g.,
826C<[0-9\x{100}]> containing code points above 255 are also now faster.
827
828=item *
829
830On platforms supporting it, several former macros are now implemented as static
831inline functions. This should speed things up slightly on non-GCC platforms.
832
833=item *
834
66f62cf6
RS
835The optimisation of hashes in boolean context has been extended to
836affect C<scalar(%hash)>, C<%hash ? ... : ...>, and C<sub { %hash || ... }>.
5ed58cbd
RS
837
838=item *
839
f105b7be 840Filetest operators manage the stack in a fractionally more efficient manner.
5ed58cbd
RS
841
842=item *
843
844Globs used in a numeric context are now numified directly in most cases,
f105b7be 845rather than being numified via stringification.
5ed58cbd
RS
846
847=item *
848
849The C<x> repetition operator is now folded to a single constant at compile
850time if called in scalar context with constant operands and no parentheses
851around the left operand.
852
853=back
854
855=head1 Modules and Pragmata
856
857=head2 New Modules and Pragmata
2426c394 858
337fb649 859=over 4
982110e0 860
82d98f72 861=item *
2426c394 862
5ed58cbd
RS
863L<Config::Perl::V> version 0.16 has been added as a dual-lifed module.
864It provides structured data retrieval of C<perl -V> output including
865information only known to the C<perl> binary and not available via L<Config>.
866
867=back
868
869=head2 Updated Modules and Pragmata
870
9863976f 871For a complete list of updates, run:
5ed58cbd 872
f105b7be 873 $ corelist --diff 5.16.0 5.18.0
5ed58cbd 874
e612b5a0 875You can substitute your favorite version in place of C<5.16.0>, too.
5ed58cbd 876
357b01df
AAS
877=over
878
879=item *
880
881L<Archive::Extract> has been upgraded from version 0.58 to 0.68.
882
883Work around an edge case on Linux with Busybox's unzip.
884
885=item *
886
887L<Archive::Tar> has been upgraded from version 1.82 to 1.90.
888
889ptar now supports the -T option as well as dashless options
890[rt.cpan.org #75473], [rt.cpan.org #75475].
891
892Auto-encode filenames marked as UTF-8 [rt.cpan.org #75474].
893
894Don't use C<tell> on L<IO::Zlib> handles [rt.cpan.org #64339].
895
896Don't try to C<chown> on symlinks.
897
898=item *
899
900L<autodie> has been upgraded from version 2.10 to 2.13.
901
902C<autodie> now plays nicely with the 'open' pragma.
903
904=item *
905
906L<B> has been upgraded from version 1.35 to 1.42.
907
908The C<stashoff> method of COPs has been added. This provides access to an
909internal field added in perl 5.16 under threaded builds [perl #113034].
910
911C<B::COP::stashpv> now supports UTF-8 package names and embedded NULs.
912
913All C<CVf_*> and C<GVf_*>
914and more SV-related flag values are now provided as constants in the C<B::>
915namespace and available for export. The default export list has not changed.
916
917This makes the module work with the new pad API.
918
919=item *
920
921L<B::Concise> has been upgraded from version 0.89 to 0.95.
922
923The C<-nobanner> option has been fixed, and C<format>s can now be dumped.
924When passed a sub name to dump, it will check also to see whether it
925is the name of a format. If a sub and a format share the same name,
926it will dump both.
927
928This adds support for the new C<OpMAYBE_TRUEBOOL> and C<OPpTRUEBOOL> flags.
929
930=item *
931
932L<B::Debug> has been upgraded from version 1.17 to 1.18.
933
934This adds support (experimentally) for C<B::PADLIST>, which will be
935added in Perl 5.17.4.
936
937=item *
938
939L<B::Deparse> has been upgraded from version 1.14_01 to 1.20.
940
941Avoid warning when run under C<perl -w>.
942
943It now deparses
944loop controls with the correct precedence, and multiple statements in a
945C<format> line are also now deparsed correctly.
946
947This release suppresses trailing semicolons in formats.
948
949This release adds stub deparsing for lexical subroutines.
950
951It no longer dies when deparsing C<sort> without arguments. It now
952correctly omits the comma for C<system $prog @args> and C<exec $prog
953@args>.
954
955=item *
956
957L<bignum>, L<bigint> and L<bigrat> have been upgraded from version 0.29 to
9580.33.
959
960The overrides for C<hex> and C<oct> have been rewritten, eliminating
961several problems, and making one incompatible change:
962
963=over
964
965=item *
966
967Formerly, whichever of C<use bigint> or C<use bigrat> was compiled later
968would take precedence over the other, causing C<hex> and C<oct> not to
969respect the other pragma when in scope.
970
971=item *
972
973Using any of these three pragmata would cause C<hex> and C<oct> anywhere
974else in the program to evalute their arguments in list context and prevent
975them from inferring $_ when called without arguments.
976
977=item *
978
979Using any of these three pragmata would make C<oct("1234")> return 1234
980(for any number not beginning with 0) anywhere in the program. Now "1234"
981is translated from octal to decimal, whether within the pragma's scope or
982not.
983
984=item *
985
986The global overrides that facilitate lexical use of C<hex> and C<oct> now
987respect any existing overrides that were in place before the new overrides
988were installed, falling back to them outside of the scope of C<use bignum>.
989
990=item *
991
992C<use bignum "hex">, C<use bignum "oct"> and similar invocations for bigint
993and bigrat now export a C<hex> or C<oct> function, instead of providing a
994global override.
995
996=back
997
998=item *
999
1000L<Carp> has been upgraded from version 1.26 to 1.28.
1001
1002Carp is no longer confused when C<caller> returns undef for a package that
1003has been deleted.
1004
1005The C<longmess()> and C<shortmess()> functions are now documented.
1006
1007=item *
1008
1009L<CGI> has been upgraded from version 3.59 to 3.63.
1010
1011Unrecognized HTML escape sequences are now handled better, problematic
1012trailing newlines are no longer inserted after E<lt>formE<gt> tags
1013by C<startform()> or C<start_form()>, and bogus "Insecure Dependency"
1014warnings appearing with some versions of perl are now worked around.
1015
1016=item *
1017
1018L<Class::Struct> has been upgraded from version 0.63 to 0.64.
1019
1020The constructor now respects overridden accessor methods [perl #29230].
1021
1022=item *
1023
1024L<Compress::Raw::Bzip2> has been upgraded from version 2.048 to 2.060.
1025
1026The misuse of Perl's "magic" API has been fixed.
1027
1028=item *
1029
1030L<Compress::Raw::Zlib> has been upgraded from version 2.048 to 2.060.
1031
1032Upgrade bundled zlib to version 1.2.7.
1033
1034Fix build failures on Irix, Solaris, and Win32, and also when building as C++
1035[rt.cpan.org #69985], [rt.cpan.org #77030], [rt.cpan.org #75222].
1036
1037The misuse of Perl's "magic" API has been fixed.
1038
1039C<compress()>, C<uncompress()>, C<memGzip()> and C<memGunzip()> have
1040been speeded up by making parameter validation more efficient.
1041
1042=item *
1043
1044L<CPAN::Meta::Requirements> has been upgraded from version 2.120630 to 2.122.
1045
1046Treat undef requirements to C<from_string_hash> as 0 (with a warning).
1047
1048Added C<requirements_for_module> method.
1049
1050=item *
1051
1052L<CPANPLUS> has been upgraded from version 0.9121 to 0.9135.
1053
1054Allow adding F<blib/script> to PATH.
1055
1056Save the history between invocations of the shell.
1057
1058Handle multiple C<makemakerargs> and C<makeflags> arguments better.
1059
1060This resolves issues with the SQLite source engine.
1061
1062=item *
1063
1064L<Data::Dumper> has been upgraded from version 2.135_06 to 2.145.
1065
1066It has been optimized to only build a seen-scalar hash as necessary,
1067thereby speeding up serialization drastically.
1068
1069Additional tests were added in order to improve statement, branch, condition
1070and subroutine coverage. On the basis of the coverage analysis, some of the
1071internals of Dumper.pm were refactored. Almost all methods are now
1072documented.
1073
1074=item *
1075
1076L<DB_File> has been upgraded from version 1.826 to 1.827.
1077
1078The main Perl module no longer uses the C<"@_"> construct.
1079
1080=item *
1081
1082L<Devel::Peek> has been upgraded from version 1.08 to 1.11.
1083
1084This fixes compilation with C++ compilers and makes the module work with
1085the new pad API.
1086
1087=item *
1088
1089L<Digest::MD5> has been upgraded from version 2.51 to 2.52.
1090
1091Fix C<Digest::Perl::MD5> OO fallback [rt.cpan.org #66634].
1092
1093=item *
1094
1095L<Digest::SHA> has been upgraded from version 5.71 to 5.84.
1096
1097This fixes a double-free bug, which might have caused vulnerabilities
1098in some cases.
1099
1100=item *
1101
1102L<DynaLoader> has been upgraded from version 1.14 to 1.18.
1103
1104This is due to a minor code change in the XS for the VMS implementation.
1105
1106This fixes warnings about using C<CODE> sections without an C<OUTPUT>
1107section.
1108
1109=item *
1110
1111L<Encode> has been upgraded from version 2.44_01 to 2.49.
1112
1113The Mac alias x-mac-ce has been added, and various bugs have been fixed
1114in Encode::Unicode, Encode::UTF7 and Encode::GSM0338.
1115
1116=item *
1117
1118L<Env> has been upgraded from version 1.03 to 1.04.
1119
1120Its SPLICE implementation no longer misbehaves in list context.
1121
1122=item *
1123
1124L<ExtUtils::CBuilder> has been upgraded from version 0.280206 to 0.280210.
1125
1126Manifest files are now correctly embedded for those versions of VC++ which
1127make use of them. [perl #111782, #111798].
1128
1129A list of symbols to export can now be passed to C<link()> when on
1130Windows, as on other OSes [perl #115100].
1131
1132=item *
1133
1134L<ExtUtils::ParseXS> has been upgraded from version 3.16 to 3.18.
1135
1136The generated C code now avoids unnecessarily incrementing
1137C<PL_amagic_generation> on Perl versions where it's done automatically
1138(or on current Perl where the variable no longer exists).
1139
1140This avoids a bogus warning for initialised XSUB non-parameters [perl
1141#112776].
1142
1143=item *
1144
1145L<File::Copy> has been upgraded from version 2.23 to 2.26.
1146
1147C<copy()> no longer zeros files when copying into the same directory,
1148and also now fails (as it has long been documented to do) when attempting
1149to copy a file over itself.
1150
1151=item *
1152
1153L<File::DosGlob> has been upgraded from version 1.06 to 1.10.
1154
1155The internal cache of file names that it keeps for each caller is now
1156freed when that caller is freed. This means
1157C<< use File::DosGlob 'glob'; eval 'scalar <*>' >> no longer leaks memory.
1158
1159=item *
1160
1161L<File::Fetch> has been upgraded from version 0.32 to 0.38.
1162
1163Added the 'file_default' option for URLs that do not have a file
1164component.
1165
1166Use C<File::HomeDir> when available, and provide C<PERL5_CPANPLUS_HOME> to
1167override the autodetection.
1168
1169Always re-fetch F<CHECKSUMS> if C<fetchdir> is set.
1170
1171=item *
1172
1173L<File::Find> has been upgraded from version 1.20 to 1.23.
1174
1175This fixes inconsistent unixy path handling on VMS.
1176
1177Individual files may now appear in list of directories to be searched
1178[perl #59750].
1179
1180=item *
1181
1182L<File::Glob> has been upgraded from version 1.17 to 1.20.
1183
1184File::Glob has had exactly the same fix as File::DosGlob. Since it is
1185what Perl's own C<glob> operator itself uses (except on VMS), this means
1186C<< eval 'scalar <*>' >> no longer leaks.
1187
1188A space-separated list of patterns return long lists of results no longer
1189results in memory corruption or crashes. This bug was introduced in
1190Perl 5.16.0. [perl #114984]
1191
1192=item *
1193
1194L<File::Spec::Unix> has been upgraded from version 3.39_02 to 3.40.
1195
1196C<abs2rel> could produce incorrect results when given two relative paths or
1197the root directory twice [perl #111510].
1198
1199=item *
1200
1201L<File::stat> has been upgraded from version 1.05 to 1.07.
1202
1203C<File::stat> ignores the L<filetest> pragma, and warns when used in
1204combination therewith. But it was not warning for C<-r>. This has been
1205fixed [perl #111640].
1206
1207C<-p> now works, and does not return false for pipes [perl #111638].
1208
1209Previously C<File::stat>'s overloaded C<-x> and C<-X> operators did not give
1210the correct results for directories or executable files when running as
1211root. They had been treating executable permissions for root just like for
1212any other user, performing group membership tests I<etc> for files not owned
1213by root. They now follow the correct Unix behaviour - for a directory they
1214are always true, and for a file if any of the three execute permission bits
1215are set then they report that root can execute the file. Perl's builtin
1216C<-x> and C<-X> operators have always been correct.
1217
1218=item *
1219
1220L<File::Temp> has been upgraded from version 0.22 to 0.23
1221
1222Fixes various bugs involving directory removal. Defers unlinking tempfiles if
1223the initial unlink fails, which fixes problems on NFS.
1224
1225=item *
1226
1227L<GDBM_File> has been upgraded from version 1.14 to 1.15.
1228
1229The undocumented optional fifth parameter to C<TIEHASH> has been
1230removed. This was intended to provide control of the callback used by
1231C<gdbm*> functions in case of fatal errors (such as filesystem problems),
1232but did not work (and could never have worked). No code on CPAN even
1233attempted to use it. The callback is now always the previous default,
1234C<croak>. Problems on some platforms with how the C<C> C<croak> function
1235is called have also been resolved.
1236
1237=item *
1238
1239L<Hash::Util> has been upgraded from version 0.11 to 0.15.
1240
1241C<hash_unlocked> and C<hashref_unlocked> now returns true if the hash is
1242unlocked, instead of always returning false [perl #112126].
1243
1244C<hash_unlocked>, C<hashref_unlocked>, C<lock_hash_recurse> and
1245C<unlock_hash_recurse> are now exportable [perl #112126].
1246
1247Two new functions, C<hash_locked> and C<hashref_locked>, have been added.
1248Oddly enough, these two functions were already exported, even though they
1249did not exist [perl #112126].
1250
1251=item *
1252
1253L<HTTP::Tiny> has been upgraded from version 0.017 to 0.025.
1254
1255Add SSL verification features [github #6], [github #9].
1256
1257Include the final URL in the response hashref.
1258
1259Add C<local_address> option.
1260
1261This improves SSL support.
1262
1263=item *
1264
1265L<IO> has been upgraded from version 1.25_06 to 1.28.
1266
1267C<sync()> can now be called on read-only file handles [perl #64772].
1268
1269L<IO::Socket> tries harder to cache or otherwise fetch socket
1270information.
1271
1272=item *
1273
1274L<IPC::Cmd> has been upgraded from version 0.76 to 0.80.
1275
1276Use C<POSIX::_exit> instead of C<exit> in C<run_forked> [rt.cpan.org #76901].
1277
1278=item *
1279
1280L<IPC::Open3> has been upgraded from version 1.12 to 1.13.
1281
1282The C<open3()> function no longer uses C<POSIX::close()> to close file
1283descriptors since that breaks the ref-counting of file descriptors done by
1284PerlIO in cases where the file descriptors are shared by PerlIO streams,
1285leading to attempts to close the file descriptors a second time when
1286any such PerlIO streams are closed later on.
1287
1288=item *
1289
1290L<Locale::Codes> has been upgraded from version 3.21 to 3.25.
1291
1292It includes some new codes.
1293
1294=item *
1295
1296L<Memoize> has been upgraded from version 1.02 to 1.03.
1297
1298Fix the C<MERGE> cache option.
1299
1300=item *
1301
1302L<Module::Build> has been upgraded from version 0.39_01 to 0.4003.
1303
1304Fixed bug where modules without C<$VERSION> might have a version of '0' listed
1305in 'provides' metadata, which will be rejected by PAUSE.
1306
1307Fixed bug in PodParser to allow numerals in module names.
1308
1309Fixed bug where giving arguments twice led to them becoming arrays, resulting
1310in install paths like F<ARRAY(0xdeadbeef)/lib/Foo.pm>.
1311
1312A minor bug fix allows markup to be used around the leading "Name" in
1313a POD "abstract" line, and some documentation improvements have been made.
1314
1315=item *
1316
1317L<Module::CoreList> has been upgraded from version 2.76_02 to 2.87
1318
1319Version information is now stored as a delta, which greatly reduces the
1320size of the F<CoreList.pm> file.
1321
1322This restores compatibility with older versions of perl and cleans up
1323the corelist data for various modules.
1324
1325=item *
1326
1327L<Module::Load::Conditional> has been upgraded from version 0.46 to 0.54.
1328
1329Fix use of C<requires> on perls installed to a path with spaces.
1330
1331Various enhancements include the new use of Module::Metadata.
1332
1333=item *
1334
1335L<Module::Metadata> has been upgraded from version 1.000009 to 1.000011.
1336
1337The creation of a Module::Metadata object for a typical module file has
1338been sped up by about 40%, and some spurious warnings about C<$VERSION>s
1339have been suppressed.
1340
1341=item *
1342
1343L<Module::Pluggable> has been upgraded from version 4.0 to 4.7.
1344
1345Amongst other changes, triggers are now allowed on events, which gives
1346a powerful way to modify behaviour.
1347
1348=item *
1349
1350L<Net::Ping> has been upgraded from version 2.38 to 2.41.
1351
1352This fixes some test failures on Windows.
1353
1354=item *
1355
1356L<Opcode> has been upgraded from version 1.23 to 1.25.
1357
1358Reflect the removal of the boolkeys opcode and the addition of the
1359clonecv, introcv and padcv opcodes.
1360
1361=item *
1362
1363L<overload> has been upgraded from version 1.18 to 1.22.
1364
1365C<no overload> now warns for invalid arguments, just like C<use overload>.
1366
1367=item *
1368
1369L<PerlIO::encoding> has been upgraded from version 0.15 to 0.16.
1370
1371This is the module implementing the ":encoding(...)" I/O layer. It no
1372longer corrupts memory or crashes when the encoding back-end reallocates
1373the buffer or gives it a typeglob or shared hash key scalar.
1374
1375=item *
1376
1377L<PerlIO::scalar> has been upgraded from version 0.14_01 to 0.16.
1378
1379The buffer scalar supplied may now only contain code pounts 0xFF or
1380lower. [perl #109828]
1381
1382=item *
1383
1384L<Perl::OSType> has been upgraded from version 1.002 to 1.003.
1385
1386This fixes a bug detecting the VOS operating system.
1387
1388=item *
1389
1390L<Pod::Html> has been upgraded from version 1.1502 to 1.18.
1391
1392The option C<--libpods> has been reinstated. It is deprecated, and its use
1393does nothing other than issue a warning that it is no longer supported.
1394
1395Since the HTML files generated by pod2html claim to have a UTF-8 charset,
1396actually write the files out using UTF-8 [perl #111446].
1397
1398=item *
1399
1400Fixed the merge of ExtUtils-MakeMaker 6.65_01 to remove an excluded
1401file. This was causing a test failure on Win32 [perl #117477]
1402
1403=item *
1404
1405L<Pod::Simple> has been upgraded from version 3.20 to 3.26.
1406
1407Numerous improvements have been made, mostly to Pod::Simple::XHTML,
1408which also has a compatibility change: the C<codes_in_verbatim> option
1409is now disabled by default. See F<cpan/Pod-Simple/ChangeLog> for the
1410full details.
1411
1412=item *
1413
1414L<re> has been upgraded from version 0.19_01 to 0.23
1415
1416Single character [class]es like C</[s]/> or C</[s]/i> are now optimized
1417as if they did not have the brackets, i.e. C</s/> or C</s/i>.
1418
1419See note about C<op_comp> in the L</Internal Changes> section below.
1420
1421=item *
1422
1423L<Safe> has been upgraded from version 2.31_01 to 2.35.
1424
1425Fix interactions with C<Devel::Cover>.
1426
1427Don't eval code under C<no strict>.
1428
1429=item *
1430
1431L<Scalar::Util> has been upgraded from version 1.25 to version 1.27.
1432
1433Fix an overloading issue with C<sum>.
1434
1435C<first> and C<reduce> now check the callback first (so C<&first(1)> is
1436disallowed).
1437
1438Fix C<tainted> on magical values [rt.cpan.org #55763].
1439
1440Fix C<sum> on previously magical values [rt.cpan.org #61118].
1441
1442Fix reading past the end of a fixed buffer [rt.cpan.org #72700].
1443
1444=item *
1445
1446L<Search::Dict> has been upgraded from version 1.04 to 1.07.
1447
1448No longer require C<stat> on filehandles.
1449
1450Use C<fc> for casefolding.
1451
1452=item *
1453
1454L<Socket> has been upgraded from version 2.001 to 2.009.
1455
1456Constants and functions required for IP multicast source group membership
1457have been added.
1458
1459C<unpack_sockaddr_in()> and C<unpack_sockaddr_in6()> now return just the IP
1460address in scalar context, and C<inet_ntop()> now guards against incorrect
1461length scalars being passed in.
1462
1463This fixes an uninitialized memory read.
1464
1465=item *
1466
1467L<Storable> has been upgraded from version 2.34 to 2.41.
1468
1469Modifying C<$_[0]> within C<STORABLE_freeze> no longer results in crashes
1470[perl #112358].
1471
1472An object whose class implements C<STORABLE_attach> is now thawed only once
1473when there are multiple references to it in the structure being thawed
1474[perl #111918].
1475
1476Restricted hashes were not always thawed correctly [perl #73972].
1477
1478Storable would croak when freezing a blessed REF object with a
1479C<STORABLE_freeze()> method [perl #113880].
1480
1481It can now freeze and thaw vstrings correctly. This causes a slight
1482incompatible change in the storage format, so the format version has
1483increased to 2.9.
1484
1485This contains various bugfixes, including compatibility fixes for older
1486versions of Perl and vstring handling.
1487
1488=item *
1489
1490L<Sys::Syslog> has been upgraded from version 0.29 to 0.32.
1491
1492This contains several bug fixes relating to C<getservbyname()>,
1493C<setlogsock()>and log levels in C<syslog()>, together with fixes for
1494Windows, Haiku-OS and GNU/kFreeBSD. See F<cpan/Sys-Syslog/Changes>
1495for the full details.
1496
1497=item *
1498
1499L<Term::ANSIColor> has been upgraded from version 3.01 to 4.02.
1500
1501Add support for italics.
1502
1503Improve error handling.
1504
1505=item *
1506
1507L<Term::ReadLine> has been upgraded from version 1.09 to 1.10. This fixes the
1508use of the B<cpan> and B<cpanp> shells on Windows in the event that the current
1509drive happens to contain a F<\dev\tty> file.
1510
1511=item *
1512
1513L<Test::Harness> has been upgraded from version 3.23 to 3.26.
1514
1515Fix glob semantics on Win32 [rt.cpan.org #49732].
1516
1517Don't use C<Win32::GetShortPathName> when calling perl [rt.cpan.org #47890].
1518
1519Ignore -T when reading shebang [rt.cpan.org #64404].
1520
1521Handle the case where we don't know the wait status of the test more
1522gracefully.
1523
1524Make the test summary 'ok' line overridable so that it can be changed to a
1525plugin to make the output of prove idempotent.
1526
1527Don't run world-writable files.
1528
1529=item *
1530
1531L<Text::Tabs> and L<Text::Wrap> have been upgraded from version 2009.0305 to
15322012.0818. Support for Unicode combining characters has been added to them
1533both.
1534
1535=item *
1536
1537L<threads::shared> has been upgraded from version 1.40 to 1.31.
1538
1539This adds the option to warn about or ignore attempts to clone structures
1540that can't be cloned, as opposed to just unconditionally dying in
1541that case.
1542
1543This adds support for dual-valued values as created by
1544L<Scalar::Util::dualvar|Scalar::Util/"dualvar NUM, STRING">.
1545
1546=item *
1547
1548L<Tie::StdHandle> has been upgraded from version 4.2 to 4.3.
1549
1550C<READ> now respects the offset argument to C<read> [perl #112826].
1551
1552=item *
1553
1554L<Time::Local> has been upgraded from version 1.2000 to 1.2300.
1555
1556Seconds values greater than 59 but less than 60 no longer cause
1557C<timegm()> and C<timelocal()> to croak.
1558
1559=item *
1560
1561L<Unicode::UCD> has been upgraded from version 0.43 to 0.53.
1562
1563This adds a function L<all_casefolds()|Unicode::UCD/all_casefolds()>
1564that returns all the casefolds.
1565
1566=item *
1567
1568L<Win32> has been upgraded from version 0.44 to 0.47.
1569
1570New APIs have been added for getting and setting the current code page.
1571
1572=back
1573
1574
5ed58cbd
RS
1575=head2 Removed Modules and Pragmata
1576
1577=over
33392251
BF
1578
1579=item *
1580
5ed58cbd
RS
1581L<Version::Requirements> has been removed from the core distribution. It is
1582available under a different name: L<CPAN::Meta::Requirements>.
2426c394 1583
337fb649 1584=back
2426c394 1585
5ed58cbd 1586=head1 Documentation
19718730 1587
5ed58cbd
RS
1588=head2 Changes to Existing Documentation
1589
1590=head3 L<perlcheat>
82d98f72 1591
5a6a30f4 1592=over 4
b7c7d786 1593
5ed58cbd
RS
1594=item *
1595
1596L<perlcheat> has been reorganized, and a few new sections were added.
1597
1598=back
1599
1600=head3 L<perldata>
1601
1602=over 4
82d98f72 1603
5ed58cbd 1604=item *
d2d1e842 1605
5ed58cbd
RS
1606Now explicitly documents the behaviour of hash initializer lists that
1607contain duplicate keys.
f355e93d 1608
5a6a30f4 1609=back
f355e93d 1610
5ed58cbd 1611=head3 L<perldiag>
19718730 1612
19718730 1613=over 4
e14ac59b 1614
5ed58cbd
RS
1615=item *
1616
1617The explanation of symbolic references being prevented by "strict refs"
1618now doesn't assume that the reader knows what symbolic references are.
1619
1620=back
9f351b45 1621
5ed58cbd 1622=head3 L<perlfaq>
9f351b45 1623
5ed58cbd 1624=over 4
9f351b45 1625
5ed58cbd 1626=item *
7cf3104f 1627
5ed58cbd 1628L<perlfaq> has been synchronized with version 5.0150040 from CPAN.
12719193 1629
6253ee75 1630=back
216cf7fc 1631
5ed58cbd 1632=head3 L<perlfunc>
f5b73711 1633
5ed58cbd
RS
1634=over 4
1635
1636=item *
a75569c0 1637
5ed58cbd 1638The return value of C<pipe> is now documented.
a75569c0 1639
5ed58cbd 1640=item *
a75569c0 1641
5ed58cbd
RS
1642Clarified documentation of C<our>.
1643
1644=back
1645
1646=head3 L<perlop>
1647
1648=over 4
1649
1650=item *
1651
1652Loop control verbs (C<dump>, C<goto>, C<next>, C<last> and C<redo>) have always
1653had the same precedence as assignment operators, but this was not documented
1654until now.
1655
1656=back
1657
1658=head3 Diagnostics
1659
1660The following additions or changes have been made to diagnostic output,
1661including warnings and fatal error messages. For the complete list of
1662diagnostic messages, see L<perldiag>.
1663
5ed58cbd
RS
1664=head2 New Diagnostics
1665
5ed58cbd
RS
1666=head3 New Errors
1667
1668=over 4
1669
1670=item *
1671
1672L<Unterminated delimiter for here document|perldiag/"Unterminated delimiter for here document">
1673
1674This message now occurs when a here document label has an initial quotation
1675mark but the final quotation mark is missing.
1676
1677This replaces a bogus and misleading error message about not finding the label
1678itself [perl #114104].
1679
1680=item *
1681
1682L<panic: child pseudo-process was never scheduled|perldiag/"panic: child pseudo-process was never scheduled">
1683
1684This error is thrown when a child pseudo-process in the ithreads implementation
1685on Windows was not scheduled within the time period allowed and therefore was
1686not able to initialize properly [perl #88840].
1687
1688=item *
1689
1690L<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/">
1691
1692This error has been added for C<(?&0)>, which is invalid. It used to
1693produce an incomprehensible error message [perl #101666].
1694
1695=item *
1696
1697L<Can't use an undefined value as a subroutine reference|perldiag/"Can't use an undefined value as %s reference">
1698
1699Calling an undefined value as a subroutine now produces this error message.
1700It used to, but was accidentally disabled, first in Perl 5.004 for
e612b5a0 1701non-magical variables, and then in Perl v5.14 for magical (e.g., tied)
5ed58cbd
RS
1702variables. It has now been restored. In the mean time, undef was treated
1703as an empty string [perl #113576].
1704
1705=item *
1706
1707L<Experimental "%s" subs not enabled|perldiag/"Experimental "%s" subs not enabled">
1708
1709To use lexical subs, you must first enable them:
1710
1711 no warnings 'experimental::lexical_subs';
1712 use feature 'lexical_subs';
1713 my sub foo { ... }
1714
1715=back
1716
1717=head3 New Warnings
1718
1719=over 4
1720
1721=item *
1722
5ed58cbd
RS
1723Strings with code points over 0xFF may not be mapped into in-memory file
1724handles
1725
1726=item *
1727
1728L<'%s' resolved to '\o{%s}%d'|perldiag/"'%s' resolved to '\o{%s}%d'">
1729
1730=item *
1731
1732L<'Trailing white-space in a charnames alias definition is deprecated'|perldiag/"Trailing white-space in a charnames alias definition is deprecated">
1733
1734=item *
1735
1736L<'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">
1737
1738=item *
1739
1740L<'Passing malformed UTF-8 to "%s" is deprecated'|perldiag/"Passing malformed UTF-8 to "%s" is deprecated">
1741
1742=item *
1743
1744L<Subroutine "&%s" is not available|perldiag/"Subroutine "&%s" is not available">
1745
1746(W closure) During compilation, an inner named subroutine or eval is
1747attempting to capture an outer lexical subroutine that is not currently
1748available. This can happen for one of two reasons. First, the lexical
1749subroutine may be declared in an outer anonymous subroutine that has not
1750yet been created. (Remember that named subs are created at compile time,
1751while anonymous subs are created at run-time.) For example,
1752
1753 sub { my sub a {...} sub f { \&a } }
1754
1755At the time that f is created, it can't capture the current the "a" sub,
1756since the anonymous subroutine hasn't been created yet. Conversely, the
1757following won't give a warning since the anonymous subroutine has by now
1758been created and is live:
1759
1760 sub { my sub a {...} eval 'sub f { \&a }' }->();
1761
1762The second situation is caused by an eval accessing a variable that has
1763gone out of scope, for example,
1764
1765 sub f {
1766 my sub a {...}
1767 sub { eval '\&a' }
1768 }
1769 f()->();
1770
1771Here, when the '\&a' in the eval is being compiled, f() is not currently
1772being executed, so its &a is not available for capture.
1773
1774=item *
1775
1776L<"%s" subroutine &%s masks earlier declaration in same %s|perldiag/"%s" subroutine &%s masks earlier declaration in same %s>
1777
1778(W misc) A "my" or "state" subroutine has been redeclared in the
1779current scope or statement, effectively eliminating all access to
1780the previous instance. This is almost always a typographical error.
1781Note that the earlier subroutine will still exist until the end of
1782the scope or until all closure references to it are destroyed.
1783
1784=item *
1785
1786L<The %s feature is experimental|perldiag/"The %s feature is experimental">
1787
1788(S experimental) This warning is emitted if you enable an experimental
1789feature via C<use feature>. Simply suppress the warning if you want
1790to use the feature, but know that in doing so you are taking the risk
1791of using an experimental feature which may change or be removed in a
1792future Perl version:
1793
1794 no warnings "experimental::lexical_subs";
1795 use feature "lexical_subs";
1796
1797=item *
1798
1799L<sleep(%u) too large|perldiag/"sleep(%u) too large">
1800
1801(W overflow) You called C<sleep> with a number that was larger than it can
1802reliably handle and C<sleep> probably slept for less time than requested.
1803
1804=item *
1805
1806L<Wide character in setenv|perldiag/"Wide character in %s">
1807
1808Attempts to put wide characters into environment variables via C<%ENV> now
1809provoke this warning.
1810
1811=item *
1812
1813"L<Invalid negative number (%s) in chr|perldiag/"Invalid negative number (%s) in chr">"
1814
1815C<chr()> now warns when passed a negative value [perl #83048].
1816
1817=item *
1818
1819"L<Integer overflow in srand|perldiag/"Integer overflow in srand">"
1820
1821C<srand()> now warns when passed a value that doesn't fit in a C<UV> (since the
1822value will be truncated rather than overflowing) [perl #40605].
1823
1824=item *
1825
1826"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">"
1827
1828Running perl with the C<-i> flag now warns if no input files are provided on
1829the command line [perl #113410].
1830
1831=back
1832
1833=head2 Changes to Existing Diagnostics
1834
1835=over 4
1836
1837=item *
1838
1839L<$* is no longer supported|perldiag/"$* is no longer supported">
1840
1841The warning that use of C<$*> and C<$#> is no longer supported is now
1842generated for every location that references them. Previously it would fail
1843to be generated if another variable using the same typeglob was seen first
1844(e.g. C<@*> before C<$*>), and would not be generated for the second and
1845subsequent uses. (It's hard to fix the failure to generate warnings at all
1846without also generating them every time, and warning every time is
1847consistent with the warnings that C<$[> used to generate.)
1848
1849=item *
1850
1851The warnings for C<\b{> and C<\B{> were added. They are a deprecation
1852warning which should be turned off by that category. One should not
1853have to turn off regular regexp warnings as well to get rid of these.
1854
1855=item *
1856
1857L<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>
1858
1859Constant overloading that returns C<undef> results in this error message.
1860For numeric constants, it used to say "Constant(undef)". "undef" has been
1861replaced with the number itself.
1862
1863=item *
1864
1865The error produced when a module cannot be loaded now includes a hint that
1866the module may need to be installed: "Can't locate hopping.pm in @INC (you
1867may need to install the hopping module) (@INC contains: ...)"
1868
1869=item *
1870
1871L<vector argument not supported with alpha versions|perldiag/vector argument not supported with alpha versions>
1872
1873This warning was not suppressable, even with C<no warnings>. Now it is
1874suppressible, and has been moved from the "internal" category to the
1875"printf" category.
1876
1877=item *
1878
1879C<< Can't do {n,m} with n > m in regex; marked by <-- HERE in m/%s/ >>
1880
1881This fatal error has been turned into a warning that reads:
1882
1883L<< Quantifier {n,m} with n > m can't match in regex | perldiag/Quantifier {n,m} with n > m can't match in regex >>
1884
1885(W regexp) Minima should be less than or equal to maxima. If you really want
1886your regexp to match something 0 times, just put {0}.
1887
1888=item *
1889
1890The "Runaway prototype" warning that occurs in bizarre cases has been
1891removed as being unhelpful and inconsistent.
1892
1893=item *
1894
1895The "Not a format reference" error has been removed, as the only case in
1896which it could be triggered was a bug.
1897
1898=item *
1899
1900The "Unable to create sub named %s" error has been removed for the same
1901reason.
1902
1903=item *
1904
1905The 'Can't use "my %s" in sort comparison' error has been downgraded to a
1906warning, '"my %s" used in sort comparison' (with 'state' instead of 'my'
1907for state variables). In addition, the heuristics for guessing whether
1908lexical $a or $b has been misused have been improved to generate fewer
1909false positives. Lexical $a and $b are no longer disallowed if they are
1910outside the sort block. Also, a named unary or list operator inside the
1911sort block no longer causes the $a or $b to be ignored [perl #86136].
1912
1913=back
1914
1915=head1 Utility Changes
1916
1917=head3 L<h2xs>
1918
1919=over 4
1920
1921=item *
1922
1923F<h2xs> no longer produces invalid code for empty defines. [perl #20636]
1924
1925=back
1926
1927=head1 Configuration and Compilation
1928
1929=over 4
1930
1931=item *
1932
1933Added C<useversionedarchname> option to Configure
1934
1935When set, it includes 'api_versionstring' in 'archname'. E.g.
1936x86_64-linux-5.13.6-thread-multi. It is unset by default.
1937
1938This feature was requested by Tim Bunce, who observed that
f105b7be 1939C<INSTALL_BASE> creates a library structure that does not
5ed58cbd
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1940differentiate by perl version. Instead, it places architecture
1941specific files in "$install_base/lib/perl5/$archname". This makes
f105b7be 1942it difficult to use a common C<INSTALL_BASE> library path with
5ed58cbd
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1943multiple versions of perl.
1944
f105b7be 1945By setting C<-Duseversionedarchname>, the $archname will be
c2959982 1946distinct for architecture I<and> API version, allowing mixed use of
f105b7be 1947C<INSTALL_BASE>.
5ed58cbd
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1948
1949=item *
1950
ff772877
RS
1951Add a C<PERL_NO_INLINE_FUNCTIONS> option
1952
f105b7be 1953If C<PERL_NO_INLINE_FUNCTIONS> is defined, don't include "inline.h"
ff772877
RS
1954
1955This permits test code to include the perl headers for definitions without
1956creating a link dependency on the perl library (which may not exist yet).
1957
1958=item *
1959
5ed58cbd
RS
1960Configure will honour the external C<MAILDOMAIN> environment variable, if set.
1961
1962=item *
1963
1964C<installman> no longer ignores the silent option
1965
1966=item *
1967
1968Both C<META.yml> and C<META.json> files are now included in the distribution.
1969
1970=item *
1971
1972F<Configure> will now correctly detect C<isblank()> when compiling with a C++
1973compiler.
1974
1975=item *
1976
1977The pager detection in F<Configure> has been improved to allow responses which
1978specify options after the program name, e.g. B</usr/bin/less -R>, if the user
1979accepts the default value. This helps B<perldoc> when handling ANSI escapes
1980[perl #72156].
1981
1982=back
1983
1984=head1 Testing
1985
1986=over 4
1987
1988=item *
1989
1990The test suite now has a section for tests that require very large amounts
1991of memory. These tests won't run by default; they can be enabled by
1992setting the C<PERL_TEST_MEMORY> environment variable to the number of
1993gibibytes of memory that may be safely used.
1994
1995=back
1996
1997=head1 Platform Support
1998
1999=head2 Discontinued Platforms
2000
2001=over 4
2002
2003=item BeOS
2004
2005BeOS was an operating system for personal computers developed by Be Inc,
2006initially for their BeBox hardware. The OS Haiku was written as an open
2007source replacement for/continuation of BeOS, and its perl port is current and
2008actively maintained.
2009
2010=item UTS Global
2011
2012Support code relating to UTS global has been removed. UTS was a mainframe
2013version of System V created by Amdahl, subsequently sold to UTS Global. The
e612b5a0 2014port has not been touched since before Perl v5.8.0, and UTS Global is now
5ed58cbd
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2015defunct.
2016
2017=item VM/ESA
2018
2019Support for VM/ESA has been removed. The port was tested on 2.3.0, which
2020IBM ended service on in March 2002. 2.4.0 ended service in June 2003, and
2021was superseded by Z/VM. The current version of Z/VM is V6.2.0, and scheduled
2022for end of service on 2015/04/30.
2023
2024=item MPE/IX
2025
2026Support for MPE/IX has been removed.
2027
2028=item EPOC
2029
2030Support code relating to EPOC has been removed. EPOC was a family of
2031operating systems developed by Psion for mobile devices. It was the
2032predecessor of Symbian. The port was last updated in April 2002.
2033
2034=item Rhapsody
2035
2036Support for Rhapsody has been removed.
2037
2038=back
2039
2040=head2 Platform-Specific Notes
2041
2042=head3 AIX
2043
2044Configure now always adds C<-qlanglvl=extc99> to the CC flags on AIX when
2045using xlC. This will make it easier to compile a number of XS-based modules
2046that assume C99 [perl #113778].
2047
2048=head3 clang++
2049
2050There is now a workaround for a compiler bug that prevented compiling
e612b5a0 2051with clang++ since Perl v5.15.7 [perl #112786].
5ed58cbd
RS
2052
2053=head3 C++
2054
2055When compiling the Perl core as C++ (which is only semi-supported), the
2056mathom functions are now compiled as C<extern "C">, to ensure proper
2057binary compatibility. (However, binary compatibility isn't generally
2058guaranteed anyway in the situations where this would matter.)
2059
2060=head3 Darwin
2061
2062Stop hardcoding an alignment on 8 byte boundaries to fix builds using
2063-Dusemorebits.
2064
2065=head3 Haiku
2066
2067Perl should now work out of the box on Haiku R1 Alpha 4.
2068
2069=head3 MidnightBSD
2070
2071C<libc_r> was removed from recent versions of MidnightBSD and older versions
2072work better with C<pthread>. Threading is now enabled using C<pthread> which
2073corrects build errors with threading enabled on 0.4-CURRENT.
2074
2075=head3 Solaris
2076
2077In Configure, avoid running sed commands with flags not supported on Solaris.
2078
2079=head3 VMS
2080
2081=over
2082
2083=item *
2084
2085Where possible, the case of filenames and command-line arguments is now
2086preserved by enabling the CRTL features C<DECC$EFS_CASE_PRESERVE> and
2087C<DECC$ARGV_PARSE_STYLE> at start-up time. The latter only takes effect
2088when extended parse is enabled in the process from which Perl is run.
2089
2090=item *
2091
2092The character set for Extended Filename Syntax (EFS) is now enabled by default
2093on VMS. Among other things, this provides better handling of dots in directory
05f5908f 2094names, multiple dots in filenames, and spaces in filenames. To obtain the old
5ed58cbd
RS
2095behavior, set the logical name C<DECC$EFS_CHARSET> to C<DISABLE>.
2096
2097=item *
2098
05f5908f 2099Fixed linking on builds configured with C<-Dusemymalloc=y>.
5ed58cbd
RS
2100
2101=item *
2102
05f5908f
CB
2103Experimental support for building Perl with the HP C++ compiler is available
2104by configuring with C<-Dusecxx>.
5ed58cbd
RS
2105
2106=item *
2107
2108All C header files from the top-level directory of the distribution are now
2109installed on VMS, providing consistency with a long-standing practice on other
2110platforms. Previously only a subset were installed, which broke non-core
2111extension builds for extensions that depended on the missing include files.
2112
2113=item *
2114
2115Quotes are now removed from the command verb (but not the parameters) for
2116commands spawned via C<system>, backticks, or a piped C<open>. Previously,
2117quotes on the verb were passed through to DCL, which would fail to recognize
2118the command. Also, if the verb is actually a path to an image or command
2119procedure on an ODS-5 volume, quoting it now allows the path to contain spaces.
2120
2121=item *
2122
2123The B<a2p> build has been fixed for the HP C++ compiler on OpenVMS.
2124
2125=back
2126
2127=head3 Win32
2128
2129=over
2130
2131=item *
2132
2133Perl can now be built using Microsoft's Visual C++ 2012 compiler by specifying
2134CCTYPE=MSVC110 (or MSVC110FREE if you are using the free Express edition for
2135Windows Desktop) in F<win32/Makefile>.
2136
2137=item *
2138
f105b7be 2139The option to build without C<USE_SOCKETS_AS_HANDLES> has been removed.
5ed58cbd
RS
2140
2141=item *
2142
2143Fixed a problem where perl could crash while cleaning up threads (including the
2144main thread) in threaded debugging builds on Win32 and possibly other platforms
2145[perl #114496].
2146
2147=item *
2148
2149A rare race condition that would lead to L<sleep|perlfunc/sleep> taking more
2150time than requested, and possibly even hanging, has been fixed [perl #33096].
2151
2152=item *
2153
2154C<link> on Win32 now attempts to set C<$!> to more appropriate values
2155based on the Win32 API error code. [perl #112272]
2156
2157Perl no longer mangles the environment block, e.g. when launching a new
2158sub-process, when the environment contains non-ASCII characters. Known
2159problems still remain, however, when the environment contains characters
2160outside of the current ANSI codepage (e.g. see the item about Unicode in
2161C<%ENV> in L<http://perl5.git.perl.org/perl.git/blob/HEAD:/Porting/todo.pod>).
2162[perl #113536]
2163
2164=item *
2165
2166Building perl with some Windows compilers used to fail due to a problem
2167with miniperl's C<glob> operator (which uses the C<perlglob> program)
2168deleting the PATH environment variable [perl #113798].
2169
2170=item *
2171
f105b7be 2172A new makefile option, C<USE_64_BIT_INT>, has been added to the Windows
5ed58cbd
RS
2173makefiles. Set this to "define" when building a 32-bit perl if you want
2174it to use 64-bit integers.
2175
2176Machine code size reductions, already made to the DLLs of XS modules in
e612b5a0 2177Perl v5.17.2, have now been extended to the perl DLL itself.
5ed58cbd 2178
e612b5a0 2179Building with VC++ 6.0 was inadvertently broken in Perl v5.17.2 but has
5ed58cbd
RS
2180now been fixed again.
2181
2182=back
2183
2184=head3 WinCE
2185
2186Building on WinCE is now possible once again, although more work is required
2187to fully restore a clean build.
2188
2189=head1 Internal Changes
2190
2191=over
2192
2193=item *
2194
4263dd11 2195Synonyms for the misleadingly named C<av_len()> have been created:
5ed58cbd
RS
2196C<av_top_index()> and C<av_tindex>. All three of these return the
2197number of the highest index in the array, not the number of elements it
2198contains.
2199
2200=item *
2201
2202SvUPGRADE() is no longer an expression. Originally this macro (and its
2203underlying function, sv_upgrade()) were documented as boolean, although
2204in reality they always croaked on error and never returned false. In 2005
2205the documentation was updated to specify a void return value, but
2206SvUPGRADE() was left always returning 1 for backwards compatibility. This
2207has now been removed, and SvUPGRADE() is now a statement with no return
2208value.
2209
2210So this is now a syntax error:
2211
2212 if (!SvUPGRADE(sv)) { croak(...); }
2213
2214If you have code like that, simply replace it with
2215
2216 SvUPGRADE(sv);
2217
237b9c6d 2218or to avoid compiler warnings with older perls, possibly
5ed58cbd
RS
2219
2220 (void)SvUPGRADE(sv);
2221
2222=item *
2223
2224Perl has a new copy-on-write mechanism that allows any SvPOK scalar to be
2225upgraded to a copy-on-write scalar. A reference count on the string buffer
d16360cf
RS
2226is stored in the string buffer itself. This feature is B<not enabled by
2227default>.
5ed58cbd 2228
d16360cf
RS
2229It can be enabled in a perl build by running F<Configure> with
2230B<-Accflags=-DPERL_NEW_COPY_ON_WRITE>, and we would encourage XS authors
2231to try their code with such an enabled perl, and provide feedback.
2232Unfortunately, there is not yet a good guide to updating XS code to cope
2233with COW. Until such a document is available, consult the perl5-porters
2234mailing list.
5ed58cbd 2235
d16360cf
RS
2236It breaks a few XS modules by allowing copy-on-write scalars to go
2237through code paths that never encountered them before.
5ed58cbd
RS
2238
2239=item *
2240
2241Copy-on-write no longer uses the SvFAKE and SvREADONLY flags. Hence,
2242SvREADONLY indicates a true read-only SV.
2243
2244Use the SvIsCOW macro (as before) to identify a copy-on-write scalar.
2245
2246=item *
2247
f105b7be 2248C<PL_glob_index> is gone.
5ed58cbd
RS
2249
2250=item *
2251
2252The private Perl_croak_no_modify has had its context parameter removed. It is
2253now has a void prototype. Users of the public API croak_no_modify remain
2254unaffected.
2255
2256=item *
2257
2258Copy-on-write (shared hash key) scalars are no longer marked read-only.
2259C<SvREADONLY> returns false on such an SV, but C<SvIsCOW> still returns
2260true.
2261
2262=item *
2263
2264A new op type, C<OP_PADRANGE> has been introduced. The perl peephole
2265optimiser will, where possible, substitute a single padrange op for a
2266pushmark followed by one or more pad ops, and possibly also skipping list
2267and nextstate ops. In addition, the op can carry out the tasks associated
f105b7be 2268with the RHS of a C<< my(...) = @_ >> assignment, so those ops may be optimised
5ed58cbd
RS
2269away too.
2270
2271=item *
2272
2273Case-insensitive matching inside a [bracketed] character class with a
2274multi-character fold no longer excludes one of the possibilities in the
2275circumstances that it used to. [perl #89774].
2276
2277=item *
2278
2279C<PL_formfeed> has been removed.
2280
2281=item *
2282
2283The regular expression engine no longer reads one byte past the end of the
2284target string. While for all internally well-formed scalars this should
2285never have been a problem, this change facilitates clever tricks with
2286string buffers in CPAN modules. [perl #73542]
2287
2288=item *
2289
2290Inside a BEGIN block, C<PL_compcv> now points to the currently-compiling
2291subroutine, rather than the BEGIN block itself.
2292
2293=item *
2294
2295C<mg_length> has been deprecated.
2296
2297=item *
2298
2299C<sv_len> now always returns a byte count and C<sv_len_utf8> a character
2300count. Previously, C<sv_len> and C<sv_len_utf8> were both buggy and would
2301sometimes returns bytes and sometimes characters. C<sv_len_utf8> no longer
be12dd22 2302assumes that its argument is in UTF-8. Neither of these creates UTF-8 caches
5ed58cbd
RS
2303for tied or overloaded values or for non-PVs any more.
2304
2305=item *
2306
2307C<sv_mortalcopy> now copies string buffers of shared hash key scalars when
2308called from XS modules [perl #79824].
2309
2310=item *
2311
2312C<RXf_SPLIT> and C<RXf_SKIPWHITE> are no longer used. They are now
2313#defined as 0.
2314
2315=item *
2316
2317The new C<RXf_MODIFIES_VARS> flag can be set by custom regular expression
2318engines to indicate that the execution of the regular expression may cause
2319variables to be modified. This lets C<s///> know to skip certain
2320optimisations. Perl's own regular expression engine sets this flag for the
2321special backtracking verbs that set $REGMARK and $REGERROR.
2322
2323=item *
2324
2325The APIs for accessing lexical pads have changed considerably.
2326
2327C<PADLIST>s are now longer C<AV>s, but their own type instead.
2328C<PADLIST>s now contain a C<PAD> and a C<PADNAMELIST> of C<PADNAME>s,
2329rather than C<AV>s for the pad and the list of pad names. C<PAD>s,
2330C<PADNAMELIST>s, and C<PADNAME>s are to be accessed as such through the
2331newly added pad API instead of the plain C<AV> and C<SV> APIs. See
2332L<perlapi> for details.
2333
2334=item *
2335
2336In the regex API, the numbered capture callbacks are passed an index
2337indicating what match variable is being accessed. There are special
2338index values for the C<$`, $&, $&> variables. Previously the same three
2339values were used to retrieve C<${^PREMATCH}, ${^MATCH}, ${^POSTMATCH}>
2340too, but these have now been assigned three separate values. See
2341L<perlreapi/Numbered capture callbacks>.
2342
2343=item *
2344
2345C<PL_sawampersand> was previously a boolean indicating that any of
2346C<$`, $&, $&> had been seen; it now contains three one-bit flags
2347indicating the presence of each of the variables individually.
2348
2349=item *
2350
2351The C<CV *> typemap entry now supports C<&{}> overloading and typeglobs,
2352just like C<&{...}> [perl #96872].
2353
2354=item *
2355
2356The C<SVf_AMAGIC> flag to indicate overloading is now on the stash, not the
2357object. It is now set automatically whenever a method or @ISA changes, so
2358its meaning has changed, too. It now means "potentially overloaded". When
2359the overload table is calculated, the flag is automatically turned off if
2360there is no overloading, so there should be no noticeable slowdown.
2361
2362The staleness of the overload tables is now checked when overload methods
2363are invoked, rather than during C<bless>.
2364
2365"A" magic is gone. The changes to the handling of the C<SVf_AMAGIC> flag
2366eliminate the need for it.
2367
2368C<PL_amagic_generation> has been removed as no longer necessary. For XS
2369modules, it is now a macro alias to C<PL_na>.
2370
2371The fallback overload setting is now stored in a stash entry separate from
2372overloadedness itself.
2373
2374=item *
2375
2376The character-processing code has been cleaned up in places. The changes
2377should be operationally invisible.
2378
2379=item *
2380
e612b5a0 2381The C<study> function was made a no-op in v5.16. It was simply disabled via
5ed58cbd
RS
2382a C<return> statement; the code was left in place. Now the code supporting
2383what C<study> used to do has been removed.
2384
2385=item *
2386
2387Under threaded perls, there is no longer a separate PV allocated for every
2388COP to store its package name (C<< cop->stashpv >>). Instead, there is an
2389offset (C<< cop->stashoff >>) into the new C<PL_stashpad> array, which
2390holds stash pointers.
2391
2392=item *
2393
2394In the pluggable regex API, the C<regexp_engine> struct has acquired a new
2395field C<op_comp>, which is currently just for perl's internal use, and
f105b7be 2396should be initialized to NULL by other regex plugin modules.
5ed58cbd
RS
2397
2398=item *
2399
7779650e 2400A new function C<alloccopstash> has been added to the API, but is considered
5ed58cbd
RS
2401experimental. See L<perlapi>.
2402
2403=item *
2404
2405Perl used to implement get magic in a way that would sometimes hide bugs in
4263dd11 2406code that could call mg_get() too many times on magical values. This hiding of
5ed58cbd
RS
2407errors no longer occurs, so long-standing bugs may become visible now. If
2408you see magic-related errors in XS code, check to make sure it, together
2409with the Perl API functions it uses, calls mg_get() only once on SvGMAGICAL()
2410values.
2411
2412=item *
2413
2414OP allocation for CVs now uses a slab allocator. This simplifies
2415memory management for OPs allocated to a CV, so cleaning up after a
2416compilation error is simpler and safer [perl #111462][perl #112312].
2417
2418=item *
2419
f105b7be 2420C<PERL_DEBUG_READONLY_OPS> has been rewritten to work with the new slab
5ed58cbd
RS
2421allocator, allowing it to catch more violations than before.
2422
2423=item *
2424
f105b7be
KE
2425The old slab allocator for ops, which was only enabled for C<PERL_IMPLICIT_SYS>
2426and C<PERL_DEBUG_READONLY_OPS>, has been retired.
5ed58cbd
RS
2427
2428=back
2429
2430=head1 Selected Bug Fixes
2431
2432=over 4
2433
2434=item *
2435
2436Here-doc terminators no longer require a terminating newline character when
2437they occur at the end of a file. This was already the case at the end of a
2438string eval [perl #65838].
2439
2440=item *
2441
f105b7be 2442C<-DPERL_GLOBAL_STRUCT> builds now free the global struct B<after>
5ed58cbd
RS
2443they've finished using it.
2444
2445=item *
2446
2447A trailing '/' on a path in @INC will no longer have an additional '/'
2448appended.
2449
2450=item *
2451
2452The C<:crlf> layer now works when unread data doesn't fit into its own
2453buffer. [perl #112244].
2454
2455=item *
2456
2457C<ungetc()> now handles UTF-8 encoded data. [perl #116322].
2458
2459=item *
2460
2461A bug in the core typemap caused any C types that map to the T_BOOL core
2462typemap entry to not be set, updated, or modified when the T_BOOL variable was
2463used in an OUTPUT: section with an exception for RETVAL. T_BOOL in an INPUT:
2464section was not affected. Using a T_BOOL return type for an XSUB (RETVAL)
2465was not affected. A side effect of fixing this bug is, if a T_BOOL is specified
2466in the OUTPUT: section (which previous did nothing to the SV), and a read only
2467SV (literal) is passed to the XSUB, croaks like "Modification of a read-only
2468value attempted" will happen. [perl #115796]
2469
2470=item *
2471
2472On many platforms, providing a directory name as the script name caused perl
2473to do nothing and report success. It should now universally report an error
2474and exit nonzero. [perl #61362]
2475
2476=item *
2477
2478C<sort {undef} ...> under fatal warnings no longer crashes. It had
e612b5a0 2479begun crashing in Perl v5.16.
5ed58cbd
RS
2480
2481=item *
2482
2483Stashes blessed into each other
2484(C<bless \%Foo::, 'Bar'; bless \%Bar::, 'Foo'>) no longer result in double
e612b5a0 2485frees. This bug started happening in Perl v5.16.
5ed58cbd
RS
2486
2487=item *
2488
2489Numerous memory leaks have been fixed, mostly involving fatal warnings and
2490syntax errors.
2491
2492=item *
2493
2494Some failed regular expression matches such as C<'f' =~ /../g> were not
2495resetting C<pos>. Also, "match-once" patterns (C<m?...?g>) failed to reset
2496it, too, when invoked a second time [perl #23180].
2497
2498=item *
2499
2500Accessing C<$&> after a pattern match now works if it had not been seen
2501before the match. I.e., this applies to C<${'&'}> (under C<no strict>) and
2502C<eval '$&'>. The same applies to C<$'> and C<$`> [perl #4289].
2503
2504=item *
2505
2506Several bugs involving C<local *ISA> and C<local *Foo::> causing stale
2507MRO caches have been fixed.
2508
2509=item *
2510
2511Defining a subroutine when its typeglob has been aliased no longer results
e612b5a0 2512in stale method caches. This bug was introduced in Perl v5.10.
5ed58cbd
RS
2513
2514=item *
2515
2516Localising a typeglob containing a subroutine when the typeglob's package
2517has been deleted from its parent stash no longer produces an error. This
e612b5a0 2518bug was introduced in Perl v5.14.
5ed58cbd
RS
2519
2520=item *
2521
2522Under some circumstances, C<local *method=...> would fail to reset method
2523caches upon scope exit.
2524
2525=item *
2526
2527C</[.foo.]/> is no longer an error, but produces a warning (as before) and
2528is treated as C</[.fo]/> [perl #115818].
2529
2530=item *
2531
2532C<goto $tied_var> now calls FETCH before deciding what type of goto
2533(subroutine or label) this is.
2534
2535=item *
2536
2537Renaming packages through glob assignment
2538(C<*Foo:: = *Bar::; *Bar:: = *Baz::>) in combination with C<m?...?> and
2539C<reset> no longer makes threaded builds crash.
2540
2541=item *
2542
2543A number of bugs related to assigning a list to hash have been fixed. Many of
2544these involve lists with repeated keys like C<(1, 1, 1, 1)>.
2545
2546=over 4
2547
2548=item *
2549
2550The expression C<scalar(%h = (1, 1, 1, 1))> now returns C<4>, not C<2>.
2551
2552=item *
2553
2554The return value of C<%h = (1, 1, 1)> in list context was wrong. Previously
2555this would return C<(1, undef, 1)>, now it returns C<(1, undef)>.
2556
2557=item *
2558
2559Perl now issues the same warning on C<($s, %h) = (1, {})> as it does for
2560C<(%h) = ({})>, "Reference found where even-sized list expected".
2561
2562=item *
2563
2564A number of additional edge cases in list assignment to hashes were
2565corrected. For more details see commit 23b7025ebc.
2566
2567=back
2568
2569=item *
2570
2571Attributes applied to lexical variables no longer leak memory.
2572[perl #114764]
2573
2574=item *
2575
2576C<dump>, C<goto>, C<last>, C<next>, C<redo> or C<require> followed by a
2577bareword (or version) and then an infix operator is no longer a syntax
2578error. It used to be for those infix operators (like C<+>) that have a
2579different meaning where a term is expected. [perl #105924]
2580
2581=item *
2582
2583C<require a::b . 1> and C<require a::b + 1> no longer produce erroneous
2584ambiguity warnings. [perl #107002]
2585
2586=item *
2587
2588Class method calls are now allowed on any string, and not just strings
2589beginning with an alphanumeric character. [perl #105922]
2590
2591=item *
2592
2593An empty pattern created with C<qr//> used in C<m///> no longer triggers
2594the "empty pattern reuses last pattern" behaviour. [perl #96230]
2595
2596=item *
2597
2598Tying a hash during iteration no longer results in a memory leak.
2599
2600=item *
2601
2602Freeing a tied hash during iteration no longer results in a memory leak.
2603
2604=item *
2605
2606List assignment to a tied array or hash that dies on STORE no longer
2607results in a memory leak.
2608
2609=item *
2610
2611If the hint hash (C<%^H>) is tied, compile-time scope entry (which copies
2612the hint hash) no longer leaks memory if FETCH dies. [perl #107000]
2613
2614=item *
2615
2616Constant folding no longer inappropriately triggers the special
2617C<split " "> behaviour. [perl #94490]
2618
2619=item *
2620
2621C<defined scalar(@array)>, C<defined do { &foo }>, and similar constructs
2622now treat the argument to C<defined> as a simple scalar. [perl #97466]
2623
2624=item *
2625
2626Running a custom debugging that defines no C<*DB::DB> glob or provides a
2627subroutine stub for C<&DB::DB> no longer results in a crash, but an error
2628instead. [perl #114990]
2629
2630=item *
2631
2632C<reset ""> now matches its documentation. C<reset> only resets C<m?...?>
2633patterns when called with no argument. An empty string for an argument now
2634does nothing. (It used to be treated as no argument.) [perl #97958]
2635
2636=item *
2637
2638C<printf> with an argument returning an empty list no longer reads past the
2639end of the stack, resulting in erratic behaviour. [perl #77094]
2640
2641=item *
2642
2643C<--subname> no longer produces erroneous ambiguity warnings.
2644[perl #77240]
2645
2646=item *
2647
2648C<v10> is now allowed as a label or package name. This was inadvertently
e612b5a0 2649broken when v-strings were added in Perl v5.6. [perl #56880]
5ed58cbd
RS
2650
2651=item *
2652
2653C<length>, C<pos>, C<substr> and C<sprintf> could be confused by ties,
2654overloading, references and typeglobs if the stringification of such
be12dd22 2655changed the internal representation to or from UTF-8. [perl #114410]
5ed58cbd
RS
2656
2657=item *
2658
2659utf8::encode now calls FETCH and STORE on tied variables. utf8::decode now
2660calls STORE (it was already calling FETCH).
2661
2662=item *
2663
2664C<$tied =~ s/$non_utf8/$utf8/> no longer loops infinitely if the tied
2665variable returns a Latin-1 string, shared hash key scalar, or reference or
2ae351f8 2666typeglob that stringifies as ASCII or Latin-1. This was a regression from
e612b5a0 2667v5.12.
5ed58cbd
RS
2668
2669=item *
2670
2671C<s///> without /e is now better at detecting when it needs to forego
2672certain optimisations, fixing some buggy cases:
2673
2674=over
2675
2676=item *
2677
2678Match variables in certain constructs (C<&&>, C<||>, C<..> and others) in
2679the replacement part; e.g., C<s/(.)/$l{$a||$1}/g>. [perl #26986]
2680
2681=item *
2682
2683Aliases to match variables in the replacement.
2684
2685=item *
2686
2687C<$REGERROR> or C<$REGMARK> in the replacement. [perl #49190]
2688
2689=item *
2690
2691An empty pattern (C<s//$foo/>) that causes the last-successful pattern to
2692be used, when that pattern contains code blocks that modify the variables
2693in the replacement.
2694
2695=back
2696
2697=item *
2698
2699The taintedness of the replacement string no longer affects the taintedness
2700of the return value of C<s///e>.
2701
2702=item *
2703
2704The C<$|> autoflush variable is created on-the-fly when needed. If this
2705happened (e.g., if it was mentioned in a module or eval) when the
2706currently-selected filehandle was a typeglob with an empty IO slot, it used
2707to crash. [perl #115206]
2708
2709=item *
2710
2711Line numbers at the end of a string eval are no longer off by one.
2712[perl #114658]
2713
2714=item *
2715
2716@INC filters (subroutines returned by subroutines in @INC) that set $_ to a
2717copy-on-write scalar no longer cause the parser to modify that string
2718buffer in place.
2719
2720=item *
2721
2722C<length($object)> no longer returns the undefined value if the object has
2723string overloading that returns undef. [perl #115260]
2724
2725=item *
2726
2727The use of C<PL_stashcache>, the stash name lookup cache for method calls, has
2728been restored,
2729
2730Commit da6b625f78f5f133 in August 2011 inadvertently broke the code that looks
2731up values in C<PL_stashcache>. As it's a only cache, quite correctly everything
2732carried on working without it.
2733
2734=item *
2735
e612b5a0 2736The error "Can't localize through a reference" had disappeared in v5.16.0
5ed58cbd 2737when C<local %$ref> appeared on the last line of an lvalue subroutine.
e612b5a0 2738This error disappeared for C<\local %$ref> in perl v5.8.1. It has now
5ed58cbd
RS
2739been restored.
2740
2741=item *
2742
2743The parsing of here-docs has been improved significantly, fixing several
2744parsing bugs and crashes and one memory leak, and correcting wrong
2745subsequent line numbers under certain conditions.
2746
2747=item *
2748
2749Inside an eval, the error message for an unterminated here-doc no longer
2750has a newline in the middle of it [perl #70836].
2751
2752=item *
2753
2754A substitution inside a substitution pattern (C<s/${s|||}//>) no longer
2755confuses the parser.
2756
2757=item *
2758
2759It may be an odd place to allow comments, but C<s//"" # hello/e> has
2760always worked, I<unless> there happens to be a null character before the
2761first #. Now it works even in the presence of nulls.
2762
2763=item *
2764
2765An invalid range in C<tr///> or C<y///> no longer results in a memory leak.
2766
2767=item *
2768
2769String eval no longer treats a semicolon-delimited quote-like operator at
2770the very end (C<eval 'q;;'>) as a syntax error.
2771
2772=item *
2773
2774C<< warn {$_ => 1} + 1 >> is no longer a syntax error. The parser used to
2775get confused with certain list operators followed by an anonymous hash and
2776then an infix operator that shares its form with a unary operator.
2777
2778=item *
2779
2780C<(caller $n)[6]> (which gives the text of the eval) used to return the
2781actual parser buffer. Modifying it could result in crashes. Now it always
2782returns a copy. The string returned no longer has "\n;" tacked on to the
2783end. The returned text also includes here-doc bodies, which used to be
2784omitted.
2785
2786=item *
2787
be12dd22
RS
2788Reset the UTF-8 position cache when accessing magical variables to avoid the
2789string buffer and the UTF-8 position cache getting out of sync
5ed58cbd
RS
2790[perl #114410].
2791
2792=item *
2793
be12dd22
RS
2794Various cases of get magic being called twice for magical UTF-8
2795strings have been fixed.
5ed58cbd
RS
2796
2797=item *
2798
2799This code (when not in the presence of C<$&> etc)
2800
2801 $_ = 'x' x 1_000_000;
2802 1 while /(.)/;
2803
2804used to skip the buffer copy for performance reasons, but suffered from C<$1>
2805etc changing if the original string changed. That's now been fixed.
2806
2807=item *
2808
2809Perl doesn't use PerlIO anymore to report out of memory messages, as PerlIO
2810might attempt to allocate more memory.
2811
2812=item *
2813
2814In a regular expression, if something is quantified with C<{n,m}> where
2815C<S<n E<gt> m>>, it can't possibly match. Previously this was a fatal
2816error, but now is merely a warning (and that something won't match).
2817[perl #82954].
2818
2819=item *
2820
2821It used to be possible for formats defined in subroutines that have
2822subsequently been undefined and redefined to close over variables in the
2823wrong pad (the newly-defined enclosing sub), resulting in crashes or
2824"Bizarre copy" errors.
2825
2826=item *
2827
2828Redefinition of XSUBs at run time could produce warnings with the wrong
2829line number.
2830
2831=item *
2832
2833The %vd sprintf format does not support version objects for alpha versions.
2834It used to output the format itself (%vd) when passed an alpha version, and
2835also emit an "Invalid conversion in printf" warning. It no longer does,
2836but produces the empty string in the output. It also no longer leaks
2837memory in this case.
2838
2839=item *
2840
2841C<< $obj->SUPER::method >> calls in the main package could fail if the
2842SUPER package had already been accessed by other means.
2843
2844=item *
2845
f105b7be 2846Stash aliasing (C<< *foo:: = *bar:: >>) no longer causes SUPER calls to ignore
5ed58cbd
RS
2847changes to methods or @ISA or use the wrong package.
2848
2849=item *
2850
2851Method calls on packages whose names end in ::SUPER are no longer treated
2852as SUPER method calls, resulting in failure to find the method.
2853Furthermore, defining subroutines in such packages no longer causes them to
2854be found by SUPER method calls on the containing package [perl #114924].
2855
2856=item *
2857
2858C<\w> now matches the code points U+200C (ZERO WIDTH NON-JOINER) and U+200D
2859(ZERO WIDTH JOINER). C<\W> no longer matches these. This change is because
2860Unicode corrected their definition of what C<\w> should match.
2861
2862=item *
2863
2864C<dump LABEL> no longer leaks its label.
2865
2866=item *
2867
2868Constant folding no longer changes the behaviour of functions like C<stat()>
2869and C<truncate()> that can take either filenames or handles.
2870C<stat 1 ? foo : bar> nows treats its argument as a file name (since it is an
2871arbitrary expression), rather than the handle "foo".
2872
2873=item *
2874
2875C<truncate FOO, $len> no longer falls back to treating "FOO" as a file name if
e612b5a0 2876the filehandle has been deleted. This was broken in Perl v5.16.0.
5ed58cbd
RS
2877
2878=item *
2879
2880Subroutine redefinitions after sub-to-glob and glob-to-glob assignments no
2881longer cause double frees or panic messages.
2882
2883=item *
2884
2885C<s///> now turns vstrings into plain strings when performing a substitution,
2886even if the resulting string is the same (C<s/a/a/>).
2887
2888=item *
2889
2890Prototype mismatch warnings no longer erroneously treat constant subs as having
2891no prototype when they actually have "".
2892
2893=item *
2894
2895Constant subroutines and forward declarations no longer prevent prototype
2896mismatch warnings from omitting the sub name.
2897
2898=item *
2899
2900C<undef> on a subroutine now clears call checkers.
2901
2902=item *
2903
e612b5a0 2904The C<ref> operator started leaking memory on blessed objects in Perl v5.16.0.
5ed58cbd
RS
2905This has been fixed [perl #114340].
2906
2907=item *
2908
2909C<use> no longer tries to parse its arguments as a statement, making
2910C<use constant { () };> a syntax error [perl #114222].
2911
2912=item *
2913
2914On debugging builds, "uninitialized" warnings inside formats no longer cause
2915assertion failures.
2916
2917=item *
2918
2919On debugging builds, subroutines nested inside formats no longer cause
2920assertion failures [perl #78550].
2921
2922=item *
2923
2924Formats and C<use> statements are now permitted inside formats.
2925
2926=item *
2927
2928C<print $x> and C<sub { print $x }-E<gt>()> now always produce the same output.
2929It was possible for the latter to refuse to close over $x if the variable was
2930not active; e.g., if it was defined outside a currently-running named
2931subroutine.
2932
2933=item *
2934
2935Similarly, C<print $x> and C<print eval '$x'> now produce the same output.
2936This also allows "my $x if 0" variables to be seen in the debugger [perl
2937#114018].
2938
2939=item *
2940
2941Formats called recursively no longer stomp on their own lexical variables, but
2942each recursive call has its own set of lexicals.
2943
2944=item *
2945
2946Attempting to free an active format or the handle associated with it no longer
2947results in a crash.
2948
2949=item *
2950
2951Format parsing no longer gets confused by braces, semicolons and low-precedence
2952operators. It used to be possible to use braces as format delimiters (instead
2953of C<=> and C<.>), but only sometimes. Semicolons and low-precedence operators
2954in format argument lines no longer confuse the parser into ignoring the line's
2955return value. In format argument lines, braces can now be used for anonymous
2956hashes, instead of being treated always as C<do> blocks.
2957
2958=item *
2959
2960Formats can now be nested inside code blocks in regular expressions and other
2961quoted constructs (C</(?{...})/> and C<qq/${...}/>) [perl #114040].
2962
2963=item *
2964
2965Formats are no longer created after compilation errors.
2966
2967=item *
2968
2969Under debugging builds, the B<-DA> command line option started crashing in Perl
e612b5a0 2970v5.16.0. It has been fixed [perl #114368].
5ed58cbd
RS
2971
2972=item *
2973
2974A potential deadlock scenario involving the premature termination of a pseudo-
2975forked child in a Windows build with ithreads enabled has been fixed. This
2976resolves the common problem of the F<t/op/fork.t> test hanging on Windows [perl
2977#88840].
2978
2979=item *
2980
5ed58cbd
RS
2981The code which generates errors from C<require()> could potentially read one or
2982two bytes before the start of the filename for filenames less than three bytes
2983long and ending C</\.p?\z/>. This has now been fixed. Note that it could
2984never have happened with module names given to C<use()> or C<require()> anyway.
2985
2986=item *
2987
2988The handling of pathnames of modules given to C<require()> has been made
2989thread-safe on VMS.
2990
2991=item *
2992
d85cd26b
RS
2993Non-blocking sockets have been fixed on VMS.
2994
2995=item *
2996
5ed58cbd
RS
2997A bug in the compilation of a C</(?{})/> expression which affected the TryCatch
2998test suite has been fixed [perl #114242].
2999
3000=item *
3001
3002Pod can now be nested in code inside a quoted construct outside of a string
3003eval. This used to work only within string evals [perl #114040].
3004
3005=item *
3006
3007C<goto ''> now looks for an empty label, producing the "goto must have
3008label" error message, instead of exiting the program [perl #111794].
3009
3010=item *
3011
3012C<goto "\0"> now dies with "Can't find label" instead of "goto must have
3013label".
3014
3015=item *
3016
3017The C function C<hv_store> used to result in crashes when used on C<%^H>
3018[perl #111000].
3019
3020=item *
3021
3022A call checker attached to a closure prototype via C<cv_set_call_checker>
3023is now copied to closures cloned from it. So C<cv_set_call_checker> now
3024works inside an attribute handler for a closure.
3025
3026=item *
3027
3028Writing to C<$^N> used to have no effect. Now it croaks with "Modification
3029of a read-only value" by default, but that can be overridden by a custom
3030regular expression engine, as with C<$1> [perl #112184].
3031
3032=item *
3033
3034C<undef> on a control character glob (C<undef *^H>) no longer emits an
3035erroneous warning about ambiguity [perl #112456].
3036
3037=item *
3038
3039For efficiency's sake, many operators and built-in functions return the
3040same scalar each time. Lvalue subroutines and subroutines in the CORE::
3041namespace were allowing this implementation detail to leak through.
3042C<print &CORE::uc("a"), &CORE::uc("b")> used to print "BB". The same thing
3043would happen with an lvalue subroutine returning the return value of C<uc>.
3044Now the value is copied in such cases.
3045
3046=item *
3047
3048C<method {}> syntax with an empty block or a block returning an empty list
3049used to crash or use some random value left on the stack as its invocant.
3050Now it produces an error.
3051
3052=item *
3053
3054C<vec> now works with extremely large offsets (E<gt>2 GB) [perl #111730].
3055
3056=item *
3057
3058Changes to overload settings now take effect immediately, as do changes to
3059inheritance that affect overloading. They used to take effect only after
3060C<bless>.
3061
3062Objects that were created before a class had any overloading used to remain
3063non-overloaded even if the class gained overloading through C<use overload>
3064or @ISA changes, and even after C<bless>. This has been fixed
3065[perl #112708].
3066
3067=item *
3068
3069Classes with overloading can now inherit fallback values.
3070
3071=item *
3072
3073Overloading was not respecting a fallback value of 0 if there were
3074overloaded objects on both sides of an assignment operator like C<+=>
3075[perl #111856].
3076
3077=item *
3078
3079C<pos> now croaks with hash and array arguments, instead of producing
3080erroneous warnings.
3081
3082=item *
3083
3084C<while(each %h)> now implies C<while(defined($_ = each %h))>, like
3085C<readline> and C<readdir>.
3086
3087=item *
3088
3089Subs in the CORE:: namespace no longer crash after C<undef *_> when called
3090with no argument list (C<&CORE::time> with no parentheses).
3091
3092=item *
3093
3094C<unpack> no longer produces the "'/' must follow a numeric type in unpack"
3095error when it is the data that are at fault [perl #60204].
3096
3097=item *
3098
3099C<join> and C<"@array"> now call FETCH only once on a tied C<$">
3100[perl #8931].
3101
3102=item *
3103
3104Some subroutine calls generated by compiling core ops affected by a
3105C<CORE::GLOBAL> override had op checking performed twice. The checking
3106is always idempotent for pure Perl code, but the double checking can
3107matter when custom call checkers are involved.
3108
3109=item *
3110
3111A race condition used to exist around fork that could cause a signal sent to
3112the parent to be handled by both parent and child. Signals are now blocked
3113briefly around fork to prevent this from happening [perl #82580].
3114
3115=item *
3116
3117The implementation of code blocks in regular expressions, such as C<(?{})>
3118and C<(??{})>, has been heavily reworked to eliminate a whole slew of bugs.
3119The main user-visible changes are:
3120
3121=over 4
3122
3123=item *
3124
3125Code blocks within patterns are now parsed in the same pass as the
3126surrounding code; in particular it is no longer necessary to have balanced
3127braces: this now works:
3128
3129 /(?{ $x='{' })/
3130
3131This means that this error message is no longer generated:
3132
3133 Sequence (?{...}) not terminated or not {}-balanced in regex
3134
3135but a new error may be seen:
3136
3137 Sequence (?{...}) not terminated with ')'
3138
3139In addition, literal code blocks within run-time patterns are only
3140compiled once, at perl compile-time:
3141
3142 for my $p (...) {
3143 # this 'FOO' block of code is compiled once,
3144 # at the same time as the surrounding 'for' loop
3145 /$p{(?{FOO;})/;
3146 }
3147
3148=item *
3149
3150Lexical variables are now sane as regards scope, recursion and closure
3151behavior. In particular, C</A(?{B})C/> behaves (from a closure viewpoint)
3152exactly like C</A/ && do { B } && /C/>, while C<qr/A(?{B})C/> is like
3153C<sub {/A/ && do { B } && /C/}>. So this code now works how you might
3154expect, creating three regexes that match 0, 1, and 2:
3155
3156 for my $i (0..2) {
3157 push @r, qr/^(??{$i})$/;
3158 }
3159 "1" =~ $r[1]; # matches
3160
3161=item *
3162
3163The C<use re 'eval'> pragma is now only required for code blocks defined
3164at runtime; in particular in the following, the text of the C<$r> pattern is
3165still interpolated into the new pattern and recompiled, but the individual
3166compiled code-blocks within C<$r> are reused rather than being recompiled,
3167and C<use re 'eval'> isn't needed any more:
3168
3169 my $r = qr/abc(?{....})def/;
3170 /xyz$r/;
3171
3172=item *
3173
3174Flow control operators no longer crash. Each code block runs in a new
3175dynamic scope, so C<next> etc. will not see
3176any enclosing loops. C<return> returns a value
3177from the code block, not from any enclosing subroutine.
3178
3179=item *
3180
3181Perl normally caches the compilation of run-time patterns, and doesn't
3182recompile if the pattern hasn't changed, but this is now disabled if
3183required for the correct behavior of closures. For example:
3184
3185 my $code = '(??{$x})';
3186 for my $x (1..3) {
3187 # recompile to see fresh value of $x each time
3188 $x =~ /$code/;
3189 }
3190
3191=item *
3192
3193The C</msix> and C<(?msix)> etc. flags are now propagated into the return
3194value from C<(??{})>; this now works:
3195
3196 "AB" =~ /a(??{'b'})/i;
3197
3198=item *
3199
3200Warnings and errors will appear to come from the surrounding code (or for
3201run-time code blocks, from an eval) rather than from an C<re_eval>:
3202
3203 use re 'eval'; $c = '(?{ warn "foo" })'; /$c/;
3204 /(?{ warn "foo" })/;
3205
3206formerly gave:
3207
3208 foo at (re_eval 1) line 1.
3209 foo at (re_eval 2) line 1.
3210
3211and now gives:
3212
3213 foo at (eval 1) line 1.
3214 foo at /some/prog line 2.
3215
3216=back
3217
3218=item *
3219
2e7bc647
KW
3220Perl now can be recompiled to use any Unicode version. In v5.16, it
3221worked on Unicodes 6.0 and 6.1, but there were various bugs if earlier
3222releases were used; the older the release the more problems.
5ed58cbd
RS
3223
3224=item *
3225
3226C<vec> no longer produces "uninitialized" warnings in lvalue context
3227[perl #9423].
3228
3229=item *
3230
3231An optimization involving fixed strings in regular expressions could cause
3232a severe performance penalty in edge cases. This has been fixed
3233[perl #76546].
3234
3235=item *
3236
3237In certain cases, including empty subpatterns within a regular expression (such
3238as C<(?:)> or C<(?:|)>) could disable some optimizations. This has been fixed.
3239
3240=item *
3241
3242The "Can't find an opnumber" message that C<prototype> produces when passed
3243a string like "CORE::nonexistent_keyword" now passes UTF-8 and embedded
3244NULs through unchanged [perl #97478].
3245
3246=item *
3247
3248C<prototype> now treats magical variables like C<$1> the same way as
3249non-magical variables when checking for the CORE:: prefix, instead of
3250treating them as subroutine names.
3251
3252=item *
3253
3254Under threaded perls, a runtime code block in a regular expression could
3255corrupt the package name stored in the op tree, resulting in bad reads
3256in C<caller>, and possibly crashes [perl #113060].
3257
3258=item *
3259
3260Referencing a closure prototype (C<\&{$_[1]}> in an attribute handler for a
3261closure) no longer results in a copy of the subroutine (or assertion
3262failures on debugging builds).
3263
3264=item *
3265
3266C<eval '__PACKAGE__'> now returns the right answer on threaded builds if
3267the current package has been assigned over (as in
3268C<*ThisPackage:: = *ThatPackage::>) [perl #78742].
3269
3270=item *
3271
3272If a package is deleted by code that it calls, it is possible for C<caller>
3273to see a stack frame belonging to that deleted package. C<caller> could
3274crash if the stash's memory address was reused for a scalar and a
3275substitution was performed on the same scalar [perl #113486].
3276
3277=item *
3278
3279C<UNIVERSAL::can> no longer treats its first argument differently
3280depending on whether it is a string or number internally.
3281
3282=item *
3283
3284C<open> with C<< <& >> for the mode checks to see whether the third argument is
3285a number, in determining whether to treat it as a file descriptor or a handle
3286name. Magical variables like C<$1> were always failing the numeric check and
3287being treated as handle names.
3288
3289=item *
3290
3291C<warn>'s handling of magical variables (C<$1>, ties) has undergone several
3292fixes. C<FETCH> is only called once now on a tied argument or a tied C<$@>
3293[perl #97480]. Tied variables returning objects that stringify as "" are
3294no longer ignored. A tied C<$@> that happened to return a reference the
3295I<previous> time it was used is no longer ignored.
3296
3297=item *
3298
3299C<warn ""> now treats C<$@> with a number in it the same way, regardless of
3300whether it happened via C<$@=3> or C<$@="3">. It used to ignore the
3301former. Now it appends "\t...caught", as it has always done with
3302C<$@="3">.
3303
3304=item *
3305
3306Numeric operators on magical variables (e.g., S<C<$1 + 1>>) used to use
3307floating point operations even where integer operations were more appropriate,
3308resulting in loss of accuracy on 64-bit platforms [perl #109542].
3309
3310=item *
3311
3312Unary negation no longer treats a string as a number if the string happened
3313to be used as a number at some point. So, if C<$x> contains the string "dogs",
3314C<-$x> returns "-dogs" even if C<$y=0+$x> has happened at some point.
3315
3316=item *
3317
e612b5a0 3318In Perl v5.14, C<-'-10'> was fixed to return "10", not "+10". But magical
5ed58cbd
RS
3319variables (C<$1>, ties) were not fixed till now [perl #57706].
3320
3321=item *
3322
3323Unary negation now treats strings consistently, regardless of the internal
3324C<UTF8> flag.
3325
3326=item *
3327
3328A regression introduced in Perl v5.16.0 involving
3329C<tr/I<SEARCHLIST>/I<REPLACEMENTLIST>/> has been fixed. Only the first
3330instance is supposed to be meaningful if a character appears more than
3331once in C<I<SEARCHLIST>>. Under some circumstances, the final instance
3332was overriding all earlier ones. [perl #113584]
3333
3334=item *
3335
3336Regular expressions like C<qr/\87/> previously silently inserted a NUL
3337character, thus matching as if it had been written C<qr/\00087/>. Now it
3338matches as if it had been written as C<qr/87/>, with a message that the
3339sequence C<"\8"> is unrecognized.
3340
3341=item *
3342
3343C<__SUB__> now works in special blocks (C<BEGIN>, C<END>, etc.).
3344
3345=item *
3346
3347Thread creation on Windows could theoretically result in a crash if done
3348inside a C<BEGIN> block. It still does not work properly, but it no longer
3349crashes [perl #111610].
3350
3351=item *
3352
3353C<\&{''}> (with the empty string) now autovivifies a stub like any other
3354sub name, and no longer produces the "Unable to create sub" error
3355[perl #94476].
3356
3357=item *
3358
3359A regression introduced in v5.14.0 has been fixed, in which some calls
3360to the C<re> module would clobber C<$_> [perl #113750].
3361
3362=item *
3363
3364C<do FILE> now always either sets or clears C<$@>, even when the file can't be
3365read. This ensures that testing C<$@> first (as recommended by the
3366documentation) always returns the correct result.
3367
3368=item *
3369
3370The array iterator used for the C<each @array> construct is now correctly
237b9c6d
SK
3371reset when C<@array> is cleared [perl #75596]. This happens, for example, when
3372the array is globally assigned to, as in C<@array = (...)>, but not when its
5ed58cbd
RS
3373B<values> are assigned to. In terms of the XS API, it means that C<av_clear()>
3374will now reset the iterator.
3375
3376This mirrors the behaviour of the hash iterator when the hash is cleared.
3377
3378=item *
3379
3380C<< $class->can >>, C<< $class->isa >>, and C<< $class->DOES >> now return
3381correct results, regardless of whether that package referred to by C<$class>
3382exists [perl #47113].
3383
3384=item *
3385
3386Arriving signals no longer clear C<$@> [perl #45173].
3387
3388=item *
3389
3390Allow C<my ()> declarations with an empty variable list [perl #113554].
3391
3392=item *
3393
3394During parsing, subs declared after errors no longer leave stubs
3395[perl #113712].
3396
3397=item *
3398
3399Closures containing no string evals no longer hang on to their containing
3400subroutines, allowing variables closed over by outer subroutines to be
3401freed when the outer sub is freed, even if the inner sub still exists
3402[perl #89544].
3403
3404=item *
3405
3406Duplication of in-memory filehandles by opening with a "<&=" or ">&=" mode
e612b5a0 3407stopped working properly in v5.16.0. It was causing the new handle to
5ed58cbd
RS
3408reference a different scalar variable. This has been fixed [perl #113764].
3409
3410=item *
3411
3412C<qr//> expressions no longer crash with custom regular expression engines
3413that do not set C<offs> at regular expression compilation time
3414[perl #112962].
3415
3416=item *
3417
3418C<delete local> no longer crashes with certain magical arrays and hashes
3419[perl #112966].
3420
3421=item *
3422
3423C<local> on elements of certain magical arrays and hashes used not to
3424arrange to have the element deleted on scope exit, even if the element did
3425not exist before C<local>.
3426
3427=item *
3428
3429C<scalar(write)> no longer returns multiple items [perl #73690].
3430
3431=item *
3432
3433String to floating point conversions no longer misparse certain strings under
3434C<use locale> [perl #109318].
3435
3436=item *
3437
3438C<@INC> filters that die no longer leak memory [perl #92252].
3439
3440=item *
3441
3442The implementations of overloaded operations are now called in the correct
3443context. This allows, among other things, being able to properly override
3444C<< <> >> [perl #47119].
3445
3446=item *
3447
3448Specifying only the C<fallback> key when calling C<use overload> now behaves
3449properly [perl #113010].
3450
3451=item *
3452
3453C<< sub foo { my $a = 0; while ($a) { ... } } >> and
3454C<< sub foo { while (0) { ... } } >> now return the same thing [perl #73618].
3455
3456=item *
3457
3458String negation now behaves the same under C<use integer;> as it does
3459without [perl #113012].
3460
3461=item *
3462
3463C<chr> now returns the Unicode replacement character (U+FFFD) for -1,
3464regardless of the internal representation. -1 used to wrap if the argument
3465was tied or a string internally.
3466
3467=item *
3468
3469Using a C<format> after its enclosing sub was freed could crash as of
e612b5a0 3470perl v5.12.0, if the format referenced lexical variables from the outer sub.
5ed58cbd
RS
3471
3472=item *
3473
3474Using a C<format> after its enclosing sub was undefined could crash as of
e612b5a0 3475perl v5.10.0, if the format referenced lexical variables from the outer sub.
5ed58cbd
RS
3476
3477=item *
3478
3479Using a C<format> defined inside a closure, which format references
3480lexical variables from outside, never really worked unless the C<write>
e612b5a0 3481call was directly inside the closure. In v5.10.0 it even started crashing.
5ed58cbd
RS
3482Now the copy of that closure nearest the top of the call stack is used to
3483find those variables.
3484
3485=item *
3486
3487Formats that close over variables in special blocks no longer crash if a
3488stub exists with the same name as the special block before the special
3489block is compiled.
3490
3491=item *
3492
3493The parser no longer gets confused, treating C<eval foo ()> as a syntax
3494error if preceded by C<print;> [perl #16249].
3495
3496=item *
3497
3498The return value of C<syscall> is no longer truncated on 64-bit platforms
3499[perl #113980].
3500
3501=item *
3502
3503Constant folding no longer causes C<print 1 ? FOO : BAR> to print to the
3504FOO handle [perl #78064].
3505
3506=item *
3507
3508C<do subname> now calls the named subroutine and uses the file name it
3509returns, instead of opening a file named "subname".
3510
3511=item *
3512
3513Subroutines looked up by rv2cv check hooks (registered by XS modules) are
3514now taken into consideration when determining whether C<foo bar> should be
3515the sub call C<foo(bar)> or the method call C<< "bar"->foo >>.
3516
3517=item *
3518
3519C<CORE::foo::bar> is no longer treated specially, allowing global overrides
3520to be called directly via C<CORE::GLOBAL::uc(...)> [perl #113016].
3521
3522=item *
3523
3524Calling an undefined sub whose typeglob has been undefined now produces the
3525customary "Undefined subroutine called" error, instead of "Not a CODE
3526reference".
3527
3528=item *
3529
3530Two bugs involving @ISA have been fixed. C<*ISA = *glob_without_array> and
3531C<undef *ISA; @{*ISA}> would prevent future modifications to @ISA from
3532updating the internal caches used to look up methods. The
e612b5a0 3533*glob_without_array case was a regression from Perl v5.12.
5ed58cbd
RS
3534
3535=item *
3536
3537Regular expression optimisations sometimes caused C<$> with C</m> to
3538produce failed or incorrect matches [perl #114068].
3539
3540=item *
3541
3542C<__SUB__> now works in a C<sort> block when the enclosing subroutine is
3543predeclared with C<sub foo;> syntax [perl #113710].
3544
3545=item *
3546
3547Unicode properties only apply to Unicode code points, which leads to
3548some subtleties when regular expressions are matched against
3549above-Unicode code points. There is a warning generated to draw your
3550attention to this. However, this warning was being generated
3551inappropriately in some cases, such as when a program was being parsed.
3552Non-Unicode matches such as C<\w> and C<[:word;]> should not generate the
3553warning, as their definitions don't limit them to apply to only Unicode
3554code points. Now the message is only generated when matching against
3555C<\p{}> and C<\P{}>. There remains a bug, [perl #114148], for the very
3556few properties in Unicode that match just a single code point. The
3557warning is not generated if they are matched against an above-Unicode
3558code point.
3559
3560=item *
3561
3562Uninitialized warnings mentioning hash elements would only mention the
3563element name if it was not in the first bucket of the hash, due to an
3564off-by-one error.
3565
3566=item *
3567
3568A regular expression optimizer bug could cause multiline "^" to behave
3569incorrectly in the presence of line breaks, such that
3570C<"/\n\n" =~ m#\A(?:^/$)#im> would not match [perl #115242].
3571
3572=item *
3573
3574Failed C<fork> in list context no longer corrupts the stack.
3575C<@a = (1, 2, fork, 3)> used to gobble up the 2 and assign C<(1, undef, 3)>
3576if the C<fork> call failed.
3577
3578=item *
3579
3580Numerous memory leaks have been fixed, mostly involving tied variables that
3581die, regular expression character classes and code blocks, and syntax
3582errors.
3583
3584=item *
3585
3586Assigning a regular expression (C<${qr//}>) to a variable that happens to
3587hold a floating point number no longer causes assertion failures on
3588debugging builds.
3589
3590=item *
3591
3592Assigning a regular expression to a scalar containing a number no longer
f105b7be 3593causes subsequent numification to produce random numbers.
5ed58cbd
RS
3594
3595=item *
3596
3597Assigning a regular expression to a magic variable no longer wipes away the
e612b5a0 3598magic. This was a regression from v5.10.
5ed58cbd
RS
3599
3600=item *
3601
3602Assigning a regular expression to a blessed scalar no longer results in
e612b5a0 3603crashes. This was also a regression from v5.10.
5ed58cbd
RS
3604
3605=item *
3606
3607Regular expression can now be assigned to tied hash and array elements with
3608flattening into strings.
3609
3610=item *
3611
f105b7be 3612Numifying a regular expression no longer results in an uninitialized
5ed58cbd
RS
3613warning.
3614
3615=item *
3616
3617Negative array indices no longer cause EXISTS methods of tied variables to
e612b5a0 3618be ignored. This was a regression from v5.12.
5ed58cbd
RS
3619
3620=item *
3621
3622Negative array indices no longer result in crashes on arrays tied to
3623non-objects.
3624
3625=item *
3626
be12dd22
RS
3627C<$byte_overload .= $utf8> no longer results in doubly-encoded UTF-8 if the
3628left-hand scalar happened to have produced a UTF-8 string the last time
5ed58cbd
RS
3629overloading was invoked.
3630
3631=item *
3632
3633C<goto &sub> now uses the current value of @_, instead of using the array
3634the subroutine was originally called with. This means
3635C<local @_ = (...); goto &sub> now works [perl #43077].
3636
3637=item *
3638
3639If a debugger is invoked recursively, it no longer stomps on its own
3640lexical variables. Formerly under recursion all calls would share the same
3641set of lexical variables [perl #115742].
3642
3643=item *
3644
3645C<*_{ARRAY}> returned from a subroutine no longer spontaneously
3646becomes empty.
3647
3648=back
3649
3650=head1 Known Problems
3651
3652=over 4
3653
3654=item *
3655
7f50b25b 3656There are no known regressions. Please report any bugs you find!
5ed58cbd
RS
3657
3658=back
3659
3660=head1 Acknowledgements
a75569c0 3661
dd38235c
RS
3662Perl v5.18.0 represents approximately 12 months of development since
3663Perl v5.16.0 and contains approximately 400,000 lines of changes across
36642,100 files from 113 authors.
3665
3666Perl continues to flourish into its third decade thanks to a vibrant
3667community of users and developers. The following people are known to
3668have contributed the improvements that became Perl v5.18.0:
3669
3670Aaron Crane, Aaron Trevena, Abhijit Menon-Sen, Adrian M. Enache, Alan
3671Haggai Alavi, Alexandr Ciornii, Andrew Tam, Andy Dougherty, Anton Nikishaev,
3672Aristotle Pagaltzis, Augustina Blair, Bob Ernst, Brad Gilbert, Breno G. de
3673Oliveira, Brian Carlson, Brian Fraser, Charlie Gonzalez, Chip Salzenberg, Chris
3674'BinGOs' Williams, Christian Hansen, Colin Kuskie, Craig A. Berry, Dagfinn
3675Ilmari Mannsåker, Daniel Dragan, Daniel Perrett, Darin McBride, Dave Rolsky,
3676David Golden, David Leadbeater, David Mitchell, David Nicol, Dominic
3677Hargreaves, E. Choroba, Eric Brine, Evan Miller, Father Chrysostomos, Florian
3678Ragwitz, François Perrad, George Greer, Goro Fuji, H.Merijn Brand, Herbert
3679Breunung, Hugo van der Sanden, Igor Zaytsev, James E Keenan, Jan Dubois,
3680Jasmine Ahuja, Jerry D. Hedden, Jess Robinson, Jesse Luehrs, Joaquin Ferrero,
3681Joel Berger, John Goodyear, John Peacock, Karen Etheridge, Karl Williamson,
3682Karthik Rajagopalan, Kent Fredric, Leon Timmermans, Lucas Holt, Lukas Mai,
3683Marcus Holland-Moritz, Markus Jansen, Martin Hasch, Matthew Horsfall, Max
3684Maischein, Michael G Schwern, Michael Schroeder, Moritz Lenz, Nicholas Clark,
3685Niko Tyni, Oleg Nesterov, Patrik Hägglund, Paul Green, Paul Johnson, Paul
3686Marquess, Peter Martini, Rafael Garcia-Suarez, Reini Urban, Renee Baecker,
3687Rhesa Rozendaal, Ricardo Signes, Robin Barker, Ronald J. Kimball, Ruslan
3688Zakirov, Salvador Fandiño, Sawyer X, Scott Lanning, Sergey Alekseev, Shawn M
3689Moore, Shirakata Kentaro, Shlomi Fish, Sisyphus, Smylers, Steffen Müller,
3690Steve Hay, Steve Peters, Steven Schubiger, Sullivan Beck, Sven Strickroth,
3691Sébastien Aperghis-Tramoni, Thomas Sibley, Tobias Leich, Tom Wyant, Tony Cook,
3692Vadim Konovalov, Vincent Pit, Volker Schatz, Walt Mankowski, Yves Orton,
3693Zefram.
3694
3695The list above is almost certainly incomplete as it is automatically generated
3696from version control history. In particular, it does not include the names of
3697the (very much appreciated) contributors who reported issues to the Perl bug
3698tracker.
3699
3700Many of the changes included in this version originated in the CPAN modules
3701included in Perl's core. We're grateful to the entire CPAN community for
3702helping Perl to flourish.
3703
3704For a more complete list of all of Perl's historical contributors, please see
3705the F<AUTHORS> file in the Perl source distribution.
f5b73711 3706
44691e6f
AB
3707=head1 Reporting Bugs
3708
e08634c5
SH
3709If you find what you think is a bug, you might check the articles recently
3710posted to the comp.lang.perl.misc newsgroup and the perl bug database at
3711http://rt.perl.org/perlbug/ . There may also be information at
3712http://www.perl.org/ , the Perl Home Page.
44691e6f 3713
e08634c5
SH
3714If you believe you have an unreported bug, please run the L<perlbug> program
3715included with your release. Be sure to trim your bug down to a tiny but
3716sufficient test case. Your bug report, along with the output of C<perl -V>,
3717will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
44691e6f
AB
3718
3719If the bug you are reporting has security implications, which make it
e08634c5
SH
3720inappropriate to send to a publicly archived mailing list, then please send it
3721to perl5-security-report@perl.org. This points to a closed subscription
3722unarchived mailing list, which includes all the core committers, who will be
3723able to help assess the impact of issues, figure out a resolution, and help
f9001595 3724co-ordinate the release of patches to mitigate or fix the problem across all
e08634c5
SH
3725platforms on which Perl is supported. Please only use this address for
3726security issues in the Perl core, not for modules independently distributed on
3727CPAN.
44691e6f
AB
3728
3729=head1 SEE ALSO
3730
e08634c5
SH
3731The F<Changes> file for an explanation of how to view exhaustive details on
3732what changed.
44691e6f
AB
3733
3734The F<INSTALL> file for how to build Perl.
3735
3736The F<README> file for general stuff.
3737
3738The F<Artistic> and F<Copying> files for copyright information.
3739
3740=cut