1UNIVERSAL::isa(3)     User Contributed Perl Documentation    UNIVERSAL::isa(3)
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NAME

6       UNIVERSAL::isa - Attempt to recover from people calling UNIVERSAL::isa
7       as a function
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SYNOPSIS

10           # from the shell
11           echo 'export PERL5OPT=-MUNIVERSAL::isa' >> /etc/profile
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13           # within your program
14           use UNIVERSAL::isa;
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16           # enable warnings for all dodgy uses of UNIVERSAL::isa
17           use UNIVERSAL::isa 'verbose';
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DESCRIPTION

20       Whenever you use "isa" in UNIVERSAL as a function, a kitten using
21       Test::MockObject dies. Normally, the kittens would be helpless, but if
22       they use UNIVERSAL::isa (the module whose docs you are reading), the
23       kittens can live long and prosper.
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25       This module replaces "UNIVERSAL::isa" with a version that makes sure
26       that, when called as a function on objects which override "isa", "isa"
27       will call the appropriate method on those objects
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29       In all other cases, the real "UNIVERSAL::isa" gets called directly.
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WARNINGS

32       If the lexical warnings pragma is available, this module will emit a
33       warning for each naughty invocation of "UNIVERSAL::isa". Silence these
34       warnings by saying:
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36           no warnings 'UNIVERSAL::isa';
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38       in the lexical scope of the naughty code.
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40       After version 1.00, warnings only appear when naughty code calls
41       UNIVERSAL::isa() as a function on an invocant for which there is an
42       overridden isa().  These are really truly active bugs, and you should
43       fix them rather than relying on this module to find them.
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45       To get warnings for all potentially dangerous uses of UNIVERSAL::isa()
46       as a function, not a method (that is, for all uses of the method as a
47       function, which are latent bugs, if not bugs that will break your code
48       as it exists now), pass the "verbose" flag when using the module.  This
49       can generate many extra warnings, but they're more specific as to the
50       actual wrong practice and they usually suggest proper fixes.
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SEE ALSO

53       UNIVERSAL::can for another discussion of the problem at hand.
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55       Test::MockObject for one example of a module that really needs to
56       override "isa()".
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58       Any decent explanation of OO to understand why calling methods as
59       functions is a staggeringly bad idea.
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AUTHORS

62       Audrey Tang <cpan@audreyt.org>
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64       chromatic <chromatic@wgz.org>
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66       Yuval Kogman <nothingmuch@woobling.org>
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69       Artistic Licence 2.0, (c) 2005 - 2009.
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73perl v5.10.1                      2010-11-12                 UNIVERSAL::isa(3)
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