UNIVERSAL - base class for ALL classes (blessed references)
use UNIVERSAL qw(isa); $yes = isa($ref, "HASH"); $io = $fd->isa("IO::Handle"); $sub = $obj->can('print');
UNIVERSAL is the base class which all bless references will inherit from, see perlobj
UNIVERSAL provides the following methods
isa returns true if
REF is blessed into package
TYPE or inherits from package
isa can be called as either a static or object method call.
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 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
VERSION can be called as either a static or object method call.
UNIVERSAL also optionally exports the following subroutines
isa returns true if the first argument is a reference and either of the following statements is true.
VALis a blessed reference and is blessed into package
TYPEor inherits from package
VALis a reference to a
TYPEof perl variable (er 'HASH')
VAL is a blessed reference which has a method called
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.