3 perlexperiment - A listing of experimental features in Perl
7 This document lists the current and past experimental features in the perl
8 core. Although all of these are documented with their appropriate topics,
9 this succinct listing gives you an overview and basic facts about their
12 So far we've merely tried to find and list the experimental features and infer
13 their inception, versions, etc. There's a lot of speculation here.
15 =head2 Current experiments
19 =item Smart match (C<~~>)
21 Introduced in Perl 5.10.0
23 Modified in Perl 5.10.1, 5.12.0
25 Using this feature triggers warnings in the category
26 C<experimental::smartmatch>.
28 The ticket for this experiment is
29 L<[perl #13173]|https://github.com/Perl/perl5/issues/13173>.
31 =item Pluggable keywords
33 Introduced in Perl 5.11.2
35 See L<perlapi/PL_keyword_plugin> for the mechanism.
37 The ticket for this experiment is
38 L<[perl #13199]|https://github.com/Perl/perl5/issues/13199>.
40 =item Regular Expression Set Operations
42 Introduced in Perl 5.18
44 Using this feature triggers warnings in the category
45 C<experimental::regex_sets>.
47 The ticket for this experiment is
48 L<[perl #13197]|https://github.com/Perl/perl5/issues/13197>.
50 See also: L<perlrecharclass/Extended Bracketed Character Classes>
52 =item Subroutine signatures
54 Introduced in Perl 5.20.0
56 Using this feature triggers warnings in the category
57 C<experimental::signatures>.
59 The ticket for this experiment is
60 L<[perl #13681]|https://github.com/Perl/perl5/issues/13681>.
62 =item Aliasing via reference
64 Introduced in Perl 5.22.0
66 Using this feature triggers warnings in the category
67 C<experimental::refaliasing>.
69 The ticket for this experiment is
70 L<[perl #14150]|https://github.com/Perl/perl5/issues/14150>.
72 See also: L<perlref/Assigning to References>
74 =item The "const" attribute
76 Introduced in Perl 5.22.0
78 Using this feature triggers warnings in the category
79 C<experimental::const_attr>.
81 The ticket for this experiment is
82 L<[perl #14428]|https://github.com/Perl/perl5/issues/14428>.
84 See also: L<perlsub/Constant Functions>
86 =item use re 'strict';
88 Introduced in Perl 5.22.0
90 Using this feature triggers warnings in the category
91 C<experimental::re_strict>.
93 The ticket for this experiment is
94 L<[perl #18755]|https://github.com/Perl/perl5/issues/18755>
96 See L<re/'strict' mode>
98 =item Declaring a reference to a variable
100 Introduced in Perl 5.26.0
102 Using this feature triggers warnings in the category
103 C<experimental::declared_refs>.
105 The ticket for this experiment is
106 L<[perl #15458]|https://github.com/Perl/perl5/issues/15458>.
108 See also: L<perlref/Declaring a Reference to a Variable>
110 =item There is an C<installhtml> target in the Makefile.
112 The ticket for this experiment is
113 L<[perl #12726]|https://github.com/Perl/perl5/issues/12726>.
115 =item (Limited) Variable-length look-behind
117 Introduced in Perl 5.30.0.
119 Variability of up to 255 characters is handled.
121 Using this feature triggers warnings in the category
122 C<experimental::vlb>.
124 The ticket for this experiment is
125 L<[perl #18756]|https://github.com/Perl/perl5/issues/18756>.
127 See also: L<perlre/(*positive_lookbehind:I<pattern>)> and
128 L<perlre/(*negative_lookbehind:I<pattern>)>
130 =item Unicode private use character hooks
132 Introduced in Perl 5.30.0.
134 This feature is part of an interface intended for internal and experimental
135 use by the perl5 developers. You are unlikely to encounter it in the wild.
137 Using this feature triggers warnings in the category
138 C<experimental::private_use>.
140 The ticket for this experiment is
141 L<[perl #18758]|https://github.com/Perl/perl5/issues/18758>.
143 =item Unicode property wildcards
145 Introduced in Perl 5.30.0.
147 This feature allows regular expression matching against Unicode character
148 properties to be expressed more concisely.
150 Using this feature triggers warnings in the category
151 C<experimental::uniprop_wildcards>.
153 The ticket for this experiment is
154 L<[perl #18759]|https://github.com/Perl/perl5/issues/18759>.
156 =item try/catch control structure
158 Introduced in Perl 5.34.0.
160 Using this feature triggers warnings in the category C<experimental::try>.
162 The ticket for this experiment is
163 L<[perl #18760]|https://github.com/Perl/perl5/issues/18760>
167 =head2 Accepted features
169 These features were so wildly successful and played so well with others that
170 we decided to remove their experimental status and admit them as full, stable
171 features in the world of Perl, lavishing all the benefits and luxuries thereof.
172 They are also awarded +5 Stability and +3 Charisma.
178 Introduced in Perl 5.005
180 =item die accepts a reference
182 Introduced in Perl 5.005
186 Introduced in Perl 5.6.0
188 See also L<perldebug>, L<perldebtut>
190 =item Weak references
192 Introduced in Perl 5.6.0
194 =item Internal file glob
196 Introduced in Perl 5.6.0
198 =item fork() emulation
200 Introduced in Perl 5.6.1
204 =item -Dusemultiplicity -Duseithreads
206 Introduced in Perl 5.6.0
208 Accepted in Perl 5.8.0
210 =item Support for long doubles
212 Introduced in Perl 5.6.0
214 Accepted in Perl 5.8.1
216 =item The C<\N> regex character class
218 The C<\N> character class, not to be confused with the named character
219 sequence C<\N{NAME}>, denotes any non-newline character in a regular
222 Introduced in Perl 5.12
224 Exact version of acceptance unclear, but no later than Perl 5.18.
226 =item C<(?{code})> and C<(??{ code })>
228 Introduced in Perl 5.6.0
230 Accepted in Perl 5.20.0
234 =item Linux abstract Unix domain sockets
236 Introduced in Perl 5.9.2
238 Accepted before Perl 5.20.0. The Socket library is now primarily maintained
239 on CPAN, rather than in the perl core.
243 =item Lvalue subroutines
245 Introduced in Perl 5.6.0
247 Accepted in Perl 5.20.0
251 =item Backtracking control verbs
255 Introduced in Perl 5.10
257 Accepted in Perl 5.20.0
259 =item The C<:pop> IO pseudolayer
261 See also L<perlrun/PERLIO>
263 Accepted in Perl 5.20.0
265 =item C<\s> in regexp matches vertical tab
267 Accepted in Perl 5.22.0
269 =item Postfix dereference syntax
271 Introduced in Perl 5.20.0
273 Accepted in Perl 5.24.0
275 =item Lexical subroutines
277 Introduced in Perl 5.18.0
279 Accepted in Perl 5.26.0
281 =item String- and number-specific bitwise operators
283 Introduced in Perl 5.22.0
285 Accepted in Perl 5.28.0
287 =item Alphabetic assertions
289 Introduced in Perl 5.28.0
291 Accepted in Perl 5.32.0
295 Introduced in Perl 5.28.0
297 Accepted in Perl 5.32.0
299 =item The infix C<isa> operator
301 Introduced in Perl 5.32.0
303 Accepted in Perl 5.36.0
307 =head2 Removed features
309 These features are no longer considered experimental and their functionality
310 has disappeared. It's your own fault if you wrote production programs using
311 these features after we explicitly told you not to (see L<perlpolicy>).
315 =item 5.005-style threading
317 Introduced in Perl 5.005
323 Introduced in Perl 5.005
325 Moved from Perl 5.9.0 to CPAN
327 =item The pseudo-hash data type
329 Introduced in Perl 5.6.0
331 Removed in Perl 5.9.0
333 =item GetOpt::Long Options can now take multiple values at once (experimental)
335 C<Getopt::Long> upgraded to version 2.35
337 Removed in Perl 5.8.8
341 The C<-A> command line switch
343 Introduced in Perl 5.9.0
345 Removed in Perl 5.9.5
347 =item Test::Harness::Straps
349 Moved from Perl 5.10.1 to CPAN
353 The experimental C<legacy> pragma was swallowed by the C<feature> pragma.
355 Introduced in Perl 5.11.2
357 Removed in Perl 5.11.3
361 Using this feature triggered warnings in the category
362 C<experimental::lexical_topic>.
364 Introduced in Perl 5.10.0
366 Removed in Perl 5.24.0
368 =item Array and hash container functions accept references
370 Using this feature triggered warnings in the category
371 C<experimental::autoderef>.
373 Superseded by L</Postfix dereference syntax>.
375 Introduced in Perl 5.14.0
377 Removed in Perl 5.24.0
379 =item C<our> can have an experimental optional attribute C<unique>
381 Introduced in Perl 5.8.0
383 Deprecated in Perl 5.10.0
385 Removed in Perl 5.28.0
387 =item The C<:win32> IO pseudolayer
389 Introduced in Perl 5.8.0 (or before)
391 Removed in Perl 5.36.0
397 For a complete list of features check L<feature>.
401 brian d foy C<< <brian.d.foy@gmail.com> >>
403 SE<eacute>bastien Aperghis-Tramoni C<< <saper@cpan.org> >>
407 Copyright 2010, brian d foy C<< <brian.d.foy@gmail.com> >>
411 You can use and redistribute this document under the same terms as Perl