http://www.perlmonks.org?node_id=915834


in reply to Re^4: Moose role with requirement consuming another role
in thread Moose role with requirement consuming another role

I think you'll like these
http://en.wikipedia.org/wiki/Abstract_type
http://c2.com/cgi/wiki?AbstractBaseClass
http://c2.com/cgi/wiki?AbstractClass
My understanding matches Arunbears, abstract classes aren't concrete, they can be a contract (virtual/interface), or actually do stuff (traits/roles), but you can't make an instance.