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lexer API fixes
[perl5.git] / pod / perl5112delta.pod
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1=head1 NAME
2
3[ Any text flagged as XXX needs to be processed before release. ]
4
5perldelta - what is new for perl v5.11.2
6
7=head1 DESCRIPTION
8
9This document describes differences between the 5.11.1 release and
10the 5.11.2 release.
11
12=head1 Notice
13
14XXX Unlikely to need this section.
15
16=head1 Incompatible Changes
17
d83f38d8 18=head2 Use of C<:=> to mean an empty attribute list is now deprecated.
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d83f38d8 20An accident of Perl's parser means that these constructions are all equivalent:
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22 my $pi := 4;
23 my $pi : = 4;
24 my $pi : = 4;
25
26with the C<:> being treated as the start of an attribute list, which ends
27before the C<=>. As whitespace is not significant here, all are parsed as an
28empty attribute list, hence all the above are equivalent to, and better written
29as
30
31 my $pi = 4;
32
33because no attribute processing is done for an empty list.
34
35As is, this means that C<:=> cannot be used as a new token, without silently
36changing the meaning of existing code. Hence that particular form is now
37deprecated, and will become a syntax error. If it is absolutely necessary to
38have empty attribute lists (for example, because of a code generator) the
39avoid the warning by adding a space before the C<=>.
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40
41=head1 Core Enhancements
42
43XXX New core language features go here. Summarise user-visible core language
44enhancements. Particularly prominent performance optimisations could go
45here, but most should go in the L</Performance Enhancements> section.
46
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47=head2 qr overloading
48
49It is now possible to overload the C<qr//> operator, that is, conversion
50to regexp, like it was already possible to overload conversion to
51boolean, string or number of objects. It is invoked when an object
52appears on the right hand side of the C<=~> operator, or when it is
53interpolated into a regexp. See L<overload>.
54
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55=head2 Pluggable keywords
56
57Extension modules can now cleanly hook into the Perl parser to define new
58kinds of keyword-headed expression and compound statement. The syntax
59following the keyword is defined entirely by the extension. This allow
60a completely non-Perl sublanguage to be parsed inline, with the right
580561a3 61ops cleanly generated. This feature is currently considered experimental.
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62
63See L<perlapi/PL_keyword_plugin> for the mechanism. The Perl core source
64distribution also includes a new module L<XS::APItest::KeywordRPN>, which
65implements reverse Polish notation arithmetic via pluggable keywords.
66This module is mainly used for test purposes, and is not normally
67installed, but also serves as an example of how to use the new mechanism.
68
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69=head2 APIs for more internals
70
71The lowest layers of the lexer and parts of the pad system now have C
72APIs available to XS extensions. These are necessary to support proper
73use of pluggable keywords, but have other uses too. The new APIs are
74experimental, and only cover a small proportion of what would be necessary
75to take full advantage of the core's facilities in these areas. It is
76intended that the Perl 5.13 development cycle will see the addition of
77a full range of clean, supported interfaces.
78
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79=head2 Overridable function lookup
80
81Where an extension module hooks the creation of rv2cv ops, to modify
82the subroutine lookup process, this now works correctly for bareword
83subroutine calls. This means that prototypes on subroutines referenced
84this way will be processed correctly. (Previously bareword subroutine
85names were initially looked up, for parsing purposes, by an unhookable
86mechanism, so extensions could only properly influence subroutine names
87that appeared with an C<&> sigil.)
88
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89=head1 New Platforms
90
91XXX List any platforms that this version of perl compiles on, that previous
92versions did not. These will either be enabled by new files in the F<hints/>
93directories, or new subdirectories and F<README> files at the top level of the
94source tree.
95
96=head1 Modules and Pragmata
97
98XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
99go here, in a list ordered by distribution name. Minimally it should be the
100module version, but it's more useful to the end user to give a paragraph's
101summary of the module's changes. In an ideal world, dual-life modules would
102have a F<Changes> file that could be cribbed.
103
104=head2 New Modules and Pragmata
105
106=over 4
107
108=item C<XXX>
109
110XXX
111
112=back
113
114=head2 Pragmata Changes
115
116=over 4
117
118=item C<XXX>
119
120XXX
121
122=back
123
124=head2 Updated Modules
125
126=over 4
127
128=item C<XXX>
129
130XXX
131
132=back
133
134=head1 Utility Changes
135
136XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go
137here. Most of these are built within the directories F<utils> and F<x2p>.
138
139=over 4
140
141=item F<XXX>
142
143XXX
144
145=back
146
147=head1 New Documentation
148
149XXX Changes which create B<new> files in F<pod/> go here.
150
151=over 4
152
153=item L<XXX>
154
155XXX
156
157=back
158
159=head1 Changes to Existing Documentation
160
161XXX Changes which significantly change existing files in F<pod/> go here.
162Any changes to F<pod/perldiag.pod> should go in L</New or Changed Diagnostics>.
163
164
165=head1 Performance Enhancements
166
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167=over 4
168
169=item *
170
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171Reversing an array to itself (as in C<@a = reverse @a>) in void context now
172happens in-place and is several orders of magnitude faster than it used to be.
173It will also preserve non-existent elements whenever possible, i.e. for non
174magical arrays or tied arrays with C<EXISTS> and C<DELETE> methods.
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175
176=back
177
178=head1 Installation and Configuration Improvements
179
180XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
181go here.
182
183=head2 Configuration improvements
184
185XXX
186
187=head2 Compilation improvements
188
189XXX
190
191=head2 Platform Specific Changes
192
193=over 4
194
195=item XXX-some-platform
196
197XXX
198
199=back
200
201=head1 Selected Bug Fixes
202
203XXX Important bug fixes in the core language are summarised here.
204Bug fixes in files in F<ext/> and F<lib/> are best summarised in
205L</Modules and Pragmata>.
206
207=over 4
208
209=item *
210
211XXX
212
213=back
214
215=head1 New or Changed Diagnostics
216
217XXX New or changed warnings emitted by the core's C<C> code go here.
218
219=over 4
220
221=item C<XXX>
222
223XXX
224
225=back
226
227=head1 Changed Internals
228
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229=over 4
230
231=item *
232
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233C<Perl_pmflag> has been removed from the public API. Calling it now generates
234a deprecation warning, and it will be removed in a future release. Although
235listed as part of the API, it was never documented, and only ever used in
236F<toke.c>, and prior to 5.10, F<regcomp.c>. In core, it has been replaced by a
237static function.
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238
239=back
240
241=head1 New Tests
242
243XXX Changes which create B<new> files in F<t/> go here. Changes to
244existing files in F<t/> aren't worth summarising, although the bugs that
245they represent may be.
246
247=over 4
248
249=item F<XXX>
250
251XXX
252
253=back
254
255=head1 Known Problems
256
257XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
258tests that had to be C<TODO>ed for the release would be noted here, unless
259they were specific to a particular platform (see below).
260
261This is a list of some significant unfixed bugs, which are regressions
262from either 5.10.1 or 5.11.1.
263
264=over 4
265
266=item *
267
268XXX
269
270=back
271
272=head1 Deprecations
273
274XXX Add any new known deprecations here.
275
276The following items are now deprecated.
277
278=over 4
279
280=item *
281
282XXX
283
284=back
285
286=head1 Platform Specific Notes
287
288XXX Any changes specific to a particular platform. VMS and Win32 are the usual
289stars here. It's probably best to group changes under the same section layout
290as the main perldelta
291
292=head1 Obituary
293
294XXX If any significant core contributor has died, we've added a short obituary
295here.
296
297=head1 Acknowledgements
298
299XXX The list of people to thank goes here.
300
301
302=head1 Reporting Bugs
303
304If you find what you think is a bug, you might check the articles
305recently posted to the comp.lang.perl.misc newsgroup and the perl
306bug database at http://rt.perl.org/perlbug/ . There may also be
307information at http://www.perl.org/ , the Perl Home Page.
308
309If you believe you have an unreported bug, please run the B<perlbug>
310program included with your release. Be sure to trim your bug down
311to a tiny but sufficient test case. Your bug report, along with the
312output of C<perl -V>, will be sent off to perlbug@perl.org to be
313analysed by the Perl porting team.
314
315If the bug you are reporting has security implications, which make it
316inappropriate to send to a publicly archived mailing list, then please send
317it to perl5-security-report@perl.org. This points to a closed subscription
318unarchived mailing list, which includes all the core committers, who be able
319to help assess the impact of issues, figure out a resolution, and help
320co-ordinate the release of patches to mitigate or fix the problem across all
321platforms on which Perl is supported. Please only use this address for
322security issues in the Perl core, not for modules independently
323distributed on CPAN.
324
325=head1 SEE ALSO
326
327The F<Changes> file for an explanation of how to view exhaustive details
328on what changed.
329
330The F<INSTALL> file for how to build Perl.
331
332The F<README> file for general stuff.
333
334The F<Artistic> and F<Copying> files for copyright information.
335
336=cut