$sub = $obj->can(method)

Checks if object $objhas a method method. If so, returns a reference to the subroutine; otherwise, returns undef. Can be called as a static or object method call, or as a subroutine:

$ref = UNIVERSAL::can(val, method)

Returns a reference to the subroutine if val is a blessed reference with a method method, and undef if val is not blessed or does not have method.

$io = $fd->isa(type)

Returns true if the reference is blessed into package type or inherits from that package. Can be called as a static or object method call, or as a subroutine:

UNIVERSAL::isa(val, type)

Returns true if the first argument is a reference and either of the following 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 (e.g., 'HASH').

VERSION([require])

Returns the value of the variable $VERSION in the package the object is blessed into. With require specified, VERSION dies if the version of the package is not equal to or greater than the version specified in require. Can be called as either a static or object method call.