wtf.rb

class A
  def foo
    "okay!"
  end

  module B
    def foo
      "not " + super
    end
  end

  module C
    def foo
      "really " + super
    end
  end
end

class X < A
  include B
  include C
end

if __FILE__ == $0
  puts X.new.foo # => prints 'really not okay'
end