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 feature is
29 L<[perl #13173]|https://github.com/Perl/perl5/issues/13173>.
31 =item Pluggable keywords
33 The ticket for this feature is
34 L<[perl #13199]|https://github.com/Perl/perl5/issues/13199>.
36 See L<perlapi/PL_keyword_plugin> for the mechanism.
38 Introduced in Perl 5.11.2
40 =item Regular Expression Set Operations
42 Introduced in Perl 5.18
44 The ticket for this feature is
45 L<[perl #13197]|https://github.com/Perl/perl5/issues/13197>.
47 See also: L<perlrecharclass/Extended Bracketed Character Classes>
49 Using this feature triggers warnings in the category
50 C<experimental::regex_sets>.
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 feature 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 feature 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 feature 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 See L<re/'strict' mode>
95 =item The <:win32> IO pseudolayer
97 The ticket for this feature is
98 L<[perl #13198]|https://github.com/Perl/perl5/issues/13198>.
100 See also L<perlrun/PERLIO>
102 =item Declaring a reference to a variable
104 Introduced in Perl 5.26.0
106 Using this feature triggers warnings in the category
107 C<experimental::declared_refs>.
109 The ticket for this feature is
110 L<[perl #15458]|https://github.com/Perl/perl5/issues/15458>.
112 See also: L<perlref/Declaring a Reference to a Variable>
114 =item There is an C<installhtml> target in the Makefile.
116 The ticket for this feature is
117 L<[perl #12726]|https://github.com/Perl/perl5/issues/12726>.
119 =item (Limited) Variable-length look-behind
121 Introduced in Perl 5.30.0. Variability of up to 255 characters is
124 Using this feature triggers warnings in the category
125 C<experimental::vlb>.
127 See also: L<perlre/(*positive_lookbehind:I<pattern>)> and
128 L<perlre/(*negative_lookbehind:I<pattern>)>
132 =head2 Accepted features
134 These features were so wildly successful and played so well with others that
135 we decided to remove their experimental status and admit them as full, stable
136 features in the world of Perl, lavishing all the benefits and luxuries thereof.
137 They are also awarded +5 Stability and +3 Charisma.
143 Introduced in Perl 5.005
145 =item die accepts a reference
147 Introduced in Perl 5.005
151 Introduced in Perl 5.6.0
153 See also L<perldebug>, L<perldebtut>
155 =item Weak references
157 Introduced in Perl 5.6.0
159 =item Internal file glob
161 Introduced in Perl 5.6.0
163 =item fork() emulation
165 Introduced in Perl 5.6.1
169 =item -Dusemultiplicity -Duseithreads
171 Introduced in Perl 5.6.0
173 Accepted in Perl 5.8.0
175 =item Support for long doubles
177 Introduced in Perl 5.6.0
179 Accepted in Perl 5.8.1
181 =item The C<\N> regex character class
183 The C<\N> character class, not to be confused with the named character
184 sequence C<\N{NAME}>, denotes any non-newline character in a regular
187 Introduced in Perl 5.12
189 Exact version of acceptance unclear, but no later than Perl 5.18.
191 =item C<(?{code})> and C<(??{ code })>
193 Introduced in Perl 5.6.0
195 Accepted in Perl 5.20.0
199 =item Linux abstract Unix domain sockets
201 Introduced in Perl 5.9.2
203 Accepted before Perl 5.20.0. The Socket library is now primarily maintained
204 on CPAN, rather than in the perl core.
208 =item Lvalue subroutines
210 Introduced in Perl 5.6.0
212 Accepted in Perl 5.20.0
216 =item Backtracking control verbs
220 Introduced in Perl 5.10
222 Accepted in Perl 5.20.0
224 =item The <:pop> IO pseudolayer
226 See also L<perlrun/PERLIO>
228 Accepted in Perl 5.20.0
230 =item C<\s> in regexp matches vertical tab
232 Accepted in Perl 5.22.0
234 =item Postfix dereference syntax
236 Introduced in Perl 5.20.0
238 Accepted in Perl 5.24.0
240 =item Lexical subroutines
242 Introduced in Perl 5.18.0
244 Accepted in Perl 5.26.0
246 =item String- and number-specific bitwise operators
248 Introduced in Perl 5.22.0
250 Accepted in Perl 5.28.0
252 =item Alphabetic assertions
254 Introduced in Perl 5.28.0
256 Accepted in Perl 5.32.0
260 Introduced in Perl 5.28.0
262 Accepted in Perl 5.32.0
266 =head2 Removed features
268 These features are no longer considered experimental and their functionality
269 has disappeared. It's your own fault if you wrote production programs using
270 these features after we explicitly told you not to (see L<perlpolicy>).
274 =item 5.005-style threading
276 Introduced in Perl 5.005
282 Introduced in Perl 5.005
284 Moved from Perl 5.9.0 to CPAN
286 =item The pseudo-hash data type
288 Introduced in Perl 5.6.0
290 Removed in Perl 5.9.0
292 =item GetOpt::Long Options can now take multiple values at once (experimental)
294 C<Getopt::Long> upgraded to version 2.35
296 Removed in Perl 5.8.8
300 The C<-A> command line switch
302 Introduced in Perl 5.9.0
304 Removed in Perl 5.9.5
306 =item Test::Harness::Straps
308 Moved from Perl 5.10.1 to CPAN
312 The experimental C<legacy> pragma was swallowed by the C<feature> pragma.
314 Introduced in Perl 5.11.2
316 Removed in Perl 5.11.3
320 Using this feature triggered warnings in the category
321 C<experimental::lexical_topic>.
323 Introduced in Perl 5.10.0
325 Removed in Perl 5.24.0
327 =item Array and hash container functions accept references
329 Using this feature triggered warnings in the category
330 C<experimental::autoderef>.
332 Superseded by L</Postfix dereference syntax>.
334 Introduced in Perl 5.14.0
336 Removed in Perl 5.24.0
338 =item C<our> can have an experimental optional attribute C<unique>
340 Introduced in Perl 5.8.0
342 Deprecated in Perl 5.10.0
344 Removed in Perl 5.28.0
350 For a complete list of features check L<feature>.
354 brian d foy C<< <brian.d.foy@gmail.com> >>
356 SE<eacute>bastien Aperghis-Tramoni C<< <saper@cpan.org> >>
360 Copyright 2010, brian d foy C<< <brian.d.foy@gmail.com> >>
364 You can use and redistribute this document under the same terms as Perl