$sub= $obj->can(method)
Checks if object $obj has a method method. If so,
returns a reference to the subroutine, otherwise returns undef.
Can be called as either a static or object method call, or
as a subroutine:
Returns a reference to the subroutine if$ref = UNIVERSAL::can(val, method)
val is a blessed reference
with a method method, and undef if
val is not blessed or does not have method.