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
       before_class_method(:monjayaki) { puts "before monjayaki, they ate modern yaki. " }
       # alias_method :modern_yaki, :monjayaki
       # def monjayaki(name)
       #    class_eval "def "+name+' ; puts " ' + name  + 'ate modern_yaki with ' + @name + '"; 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