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
isareturns true if
REFis blessed into package
TYPEor inherits from package
isa can be called as either a static or object method call.
canchecks 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.
VERSIONwill return the value of the variable
$VERSIONin the package the object is blessed into. If
REQUIREis 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.
can methods can also be called as subroutines
isareturns 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
or inherits from package
VAL is a reference to a
TYPE of perl variable (er
VALis a blessed reference which has a method called
canreturns a reference to the subroutine. If
VALis 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.
If rather than formatting bugs, you encounter substantive content errors in these documents, such as mistakes in the explanations or code, please use the perlbug utility included with the Perl distribution.