Ruby 2.0 was (and hopefully still) earmarked to have traits which are an enhancement on mixins providing a much better & refined compositional implementation.
Traits are an improvement to mixins. IIRC Matz gave a talk (RubyConf 2010?) where he describes the proposed traits implementation. Here's one set of slides (not Matz's talk) which also shows
some traits examples - http://www.slideshare.net/fabiokung/ruby-20-to-infinity-and-...
Thus it (should) allow you to do things like excluding or renaming methods/traits ala Perl roles - https://metacpan.org/module/Moose::Manual::Roles#METHOD-EXCL...