Support multimethods and subroutine overloading in Perl

 Sometimes Perl's standard polymorphic method dispatch mechanism isn't
 sophisticated enough to cope with the complexities of finding the right
 method to handle a given situation.
 .
 Generally speaking, multiple dispatch is needed whenever two or more objects
 belonging to different class hierarchies are going to interact, and we need to
 do different things depending on the combination of actual types of those
 objects. Typical applications that need this kind of ability include graphical
 user interfaces, image processing libraries, mixed-precision numerical
 computation systems, and most types of simulations.