gistfile1.rb

require 'rubygems'
require 'facets'

module Creme  
  def cost
    puts "before_filter"
    super
  end
end

class Coffee
  prepend Creme
  
  def cost
    puts "3"
  end
end

coffee = Coffee.new
coffee.cost



#But guess what, it's by overriding new:

# facet library
  def prepend( aspect )
    _new      = method(:new)
    _allocate = method(:allocate)
    (class << self; self; end).class_eval do
      define_method(:new) do |*args|
        o = _new.call(*args)
        o.extend aspect
        o
      end
      define_method(:allocate) do |*args|
        o = _allocate.call(*args)
        o.extend aspect
        o
      end
    end
  end