hook.rb

#!/usr/bin/env ruby

require 'rubygems'
require 'extlib'

####################################################
module Baz
  module Extension
    class << self
      def included(base)
        base.send :extend , Base
      end
    end

    module Base
      def monjayaki(man)
        class_eval <<-EOS
          def #{man}
            puts "#{man} ate monjayaki with " + @name
          end
EOS
      end
    end

  end
end

####################################################
module Bar
  class << self
    def included(base)
     base.class_eval <<-EOF
       include Baz::Extension
       include Extlib::Hook
       class << self
        alias_method :monjayaki_without_modern, :monjayaki
        def monjayaki(man)
          self.class_eval 'def '+ man +
                          '; puts " and ' +
                          man + ' ate modern yaki" ; end' 
        end
       end
EOF
   end
  end
end

####################################################
class Foo
  include Bar

  def initialize(name)
    @name = name
  end

  def greet(greet="")
    puts "#{greet} #{@name} "
  end

  monjayaki('mike')
end

foo = Foo.new("john")
foo.greet("hello!")
foo.mike