UNIVERSAL(3)

NAME
UNIVERSAL - base class for ALL classes (blessed references)

SYNOPSIS

    $io = $fd->isa("IO::Handle");
    $sub = $obj->can('print');
    $yes = UNIVERSAL::isa($ref, "HASH");

DESCRIPTION
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 package TYPE.

    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 returned.

    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.