CLOS and Perl 6 have multiple dispatch, which improves genericity when used well. All four of the languages I mentioned have better metaprogramming capabilitie

CLOS and Perl 6 have multiple dispatch, which improves genericity when used well. All four of the languages I mentioned have better metaprogramming capabilities, whether from runtime introspection in Smalltalk to a well-defined MOP in the other three. Smalltalk and both Perls offer better mechanisms for genericity, abstraction, and safety through traits and roles.