mixin.rb

module Mod1
  def hello
    puts "Hello from Mod1"
    end
end

module Mod2
  def hello
    puts "Hello from Mod2"
  end
end

class Cls1
  include Mod1
  alias hello_from_mod1 hello
  include Mod2
  alias hello hello_from_mod1
end

Cls1.new.hello # => Hello from Mod1