nyan.rb

# -*- coding: utf-8 -*-

module Nyan
  def nyan
    puts "いんすたんすだにゃーん"
  end

  class << self
    def included(klass)
      klass.extend(ClassMethods)
    end
  end

  module ClassMethods
    def nyan
      puts "くらすだにゃーん"
    end
  end
end

class Human
  include Nyan
end
  
Human.nyan
# => くらすだにゃーん

Human.new.nyan
# => いんすたんすだにゃーん