gistfile1.builder

class A
  def a
    'a'
  end
end

module M extend self

  class A
    def a
      "evil is here!"
    end
  end

  def m
    A.new.a
  end
end

module N extend self
  include M
  def n
    A.new.a
  end
end

> M.m
=> "evil is here!"
> N.n
=> "evil is here!"
> A.new.a
=> "a"


# Too bad it doesn't work for basic types, this way we could eliminate monkeypatching damage. 
# Well, it could actually work, but you need to explicitly do String.new, Hash.new etc.