experimental - Experimental features made easy


   version 0.016


    use experimental 'lexical_subs', 'smartmatch';
    my sub foo { $_[0] ~~ 1 }


   This pragma provides an easy and convenient way to enable or disable
   experimental features.

   Every version of perl has some number of features present but
   considered "experimental."  For much of the life of Perl 5, this was
   only a designation found in the documentation.  Starting in Perl
   v5.10.0, and more aggressively in v5.18.0, experimental features were
   placed behind pragmata used to enable the feature and disable
   associated warnings.

   The "experimental" pragma exists to combine the required incantations
   into a single interface stable across releases of perl.  For every
   experimental feature, this should enable the feature and silence
   warnings for the enclosing lexical scope:

     use experimental 'feature-name';

   To disable the feature and, if applicable, re-enable any warnings, use:

     no experimental 'feature-name';

   The supported features, documented further below, are:

           array_base    - allow the use of $[ to change the starting index of @array
           autoderef     - allow push, each, keys, and other built-ins on references
           lexical_topic - allow the use of lexical $_ via "my $_"
           postderef     - allow the use of postfix dereferencing expressions, including
                           in interpolating strings
           refaliasing   - allow aliasing via \$x = \$y
           regex_sets    - allow extended bracketed character classes in regexps
           signatures    - allow subroutine signatures (for named arguments)
           smartmatch    - allow the use of ~~
           switch        - allow the use of ~~, given, and when

   Ordering matters
   Using this pragma to 'enable an experimental feature' is another way of
   saying that this pragma will disable the warnings which would result
   from using that feature.  Therefore, the order in which pragmas are
   applied is important.  In particular, you probably want to enable
   experimental features after you enable warnings:

     use warnings;
     use experimental 'smartmatch';

   You also need to take care with modules that enable warnings for you.
   A common example being Moose.  In this example, warnings for the
   'smartmatch' feature are first turned on by the warnings pragma, off by
   the experimental pragma and back on again by the Moose module (fix is
   to switch the last two lines):

     use warnings;
     use experimental 'smartmatch';
     use Moose;

   Because of the nature of the features it enables, forward compatibility
   can not be guaranteed in any way.


   Leon Timmermans <leont@cpan.org>


   This software is copyright (c) 2013 by Leon Timmermans.

   This is free software; you can redistribute it and/or modify it under
   the same terms as the Perl 5 programming language system itself.


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