Based on tenderlove’s which tenderlovemaking.com/2011/12/05/profiling-rails-startup-with-dtrace/

Base Use: > require ‘rwhich/file’ > File.which ‘ls’

> “/bin/ls”

> File.which ‘hahahahahah’ assuming you don’t have a hahahahahah executable in ENV

> nil

Other Use: > require ‘rwhich’ > Class Foo

  extend RWhich
end

> Foo.which ‘ls’

> “/bin/ls”

> Class Bar

  include RWhich
end

> bar = Bar.new > bar.which ‘ls’

> “/bin/ls”