The special class
UNIVERSAL contains methods that are automatically inherited by all other classes:
Returns a reference to the method if its invocant has it, undef otherwise.
Checks if the object or class performs the given role.
Returns true if its invocant is class, or any class inheriting from class.
Returns the version of its invocant. Checks the version if need is supplied.
These methods can be used as normal functions as well, e.g.,
CORE provides access to all Perl built-in functions, even when they have been overridden.
SUPER provides access to base class methods without having to specify which class defined that method. This is meaningful only when used inside a method.