gistfile1.rb

module Beer
  def drink
    "gulp"
  end
end

class Mug
  include Beer
end

module Lime
  def add_lime
    "mmm"
  end
end

Beer.send :include, Lime

Mug.new.add_lime
# NoMethodError: undefined method `add_lime' for #<Mug:0x507f8>
#   from (irb):19
#   from :0