example_mixin.rb

module Comparable
  def hola
    puts "hola jose"
  end
end

class Person
  include Comparable
end

Person.new.hola 
  #=> "hola jose"


module Comparable
  class Person
    def hola
      puts "hola dentro del comparable"
    end
  end
end

Comparable::Person.new.hola
  # => "hola dentro del comparable"