UNIVERSAL::isa(3)     User Contributed Perl Documentation    UNIVERSAL::isa(3)


NAME
       UNIVERSAL::isa - Attempt to recover from people calling UNIVERSAL::isa
       as a function

VERSION
       version 1.20171012

SYNOPSIS
           # from the shell
           echo 'export PERL5OPT=-MUNIVERSAL::isa' >> /etc/profile

           # within your program
           use UNIVERSAL::isa;

           # enable warnings for all dodgy uses of UNIVERSAL::isa
           use UNIVERSAL::isa 'verbose';

DESCRIPTION
       Whenever you use "isa" in UNIVERSAL as a function, a kitten using
       Test::MockObject dies. Normally, the kittens would be helpless, but if
       they use UNIVERSAL::isa (the module whose docs you are reading), the
       kittens can live long and prosper.

       This module replaces "UNIVERSAL::isa" with a version that makes sure
       that, when called as a function on objects which override "isa", "isa"
       will call the appropriate method on those objects

       In all other cases, the real "UNIVERSAL::isa" gets called directly.

       NOTE: You should use this module only for debugging purposes. It does
       not belong as a dependency in running code.

FUNCTIONS
   original_isa
       This sub contains the definition of the original "UNIVERSAL::isa"
       definition, in case you need it.

WARNINGS
       If the lexical warnings pragma is available, this module will emit a
       warning for each naughty invocation of "UNIVERSAL::isa". Silence these
       warnings by saying:

           no warnings 'UNIVERSAL::isa';

       in the lexical scope of the naughty code.

       After version 1.00, warnings only appear when naughty code calls
       UNIVERSAL::isa() as a function on an invocant for which there is an
       overridden isa().  These are really truly active bugs, and you should
       fix them rather than relying on this module to find them.

       To get warnings for all potentially dangerous uses of UNIVERSAL::isa()
       as a function, not a method (that is, for all uses of the method as a
       function, which are latent bugs, if not bugs that will break your code
       as it exists now), pass the "verbose" flag when using the module.  This
       can generate many extra warnings, but they're more specific as to the
       actual wrong practice and they usually suggest proper fixes.

SEE ALSO
       Perl::Critic::Policy::BuiltinFunctions::ProhibitUniversalIsa

       UNIVERSAL::can for another discussion of the problem at hand.

       Test::MockObject for one example of a module that really needs to
       override "isa()".

       Any decent explanation of OO to understand why calling methods as
       functions is a staggeringly bad idea.

SUPPORT
       Bugs may be submitted through the RT bug tracker
       <https://rt.cpan.org/Public/Dist/Display.html?Name=UNIVERSAL-isa> (or
       bug-UNIVERSAL-isa@rt.cpan.org <mailto:bug-UNIVERSAL-isa@rt.cpan.org>).

AUTHORS
       o   Audrey Tang <cpan@audreyt.org>

       o   chromatic <chromatic@wgz.org>

       o   <?><?><?><?> <?><?><?>'<?><?> (Yuval Kogman)
           <nothingmuch@woobling.org>

CONTRIBUTORS
       o   Karen Etheridge <ether@cpan.org>

       o   Graham Knop <haarg@haarg.org>

       o   Ricardo Signes <rjbs@cpan.org>

COPYRIGHT AND LICENCE
       This software is copyright (c) 2011 by chromatic@wgz.org.

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

perl v5.32.0                      2020-07-07                 UNIVERSAL::isa(3)