UNIVERSAL - base class for ALL classes (blessed references)
$io = $fd->isa("IO::Handle");
$sub = $obj->can('print');
$yes = UNIVERSAL::isa($ref, "HASH");
UNIVERSAL is the base class which all bless references will inherit from,
see the perlobj manpage
UNIVERSAL provides the following methods
isa ( TYPE )
isa returns true if REF is blessed into package TYPE or inherits from
isa can be called as either a static or object method call.
can ( METHOD )
can checks if the object has a method called METHOD. If it does then
a reference to the sub is returned. If it does not then undef is
can can be called as either a static or object method call.
VERSION ( [ REQUIRE ] )
VERSION will return the value of the variable $VERSION in the package
the object is blessed into. If REQUIRE is given then it will do a
comparison and die if the package version is not greater than or
equal to REQUIRE.
VERSION can be called as either a static or object method call.
The isa and can methods can also be called as subroutines
UNIVERSAL::isa ( VAL, TYPE )
isa returns true if the first argument is a reference and either of
the following statements is true.
VAL is a blessed reference and is blessed into package TYPE
or inherits from package TYPE
VAL is a reference to a TYPE of perl variable (er 'HASH')
UNIVERSAL::can ( VAL, METHOD )
If VAL is a blessed reference which has a method called METHOD, can
returns a reference to the subroutine. If VAL is not a blessed
reference, or if it does not have a method METHOD, undef is returned.
These subroutines should not be imported via use UNIVERSAL qw(...). If
you want simple local access to them you can do
*isa = \&UNIVERSAL::isa;
to import isa into your package.
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