metaprogramming with modules in ruby This will only work with ruby 2.0 http://ruby-doc.org/core-2.0/Module.html#method-i-prepend

meta_module3.rb

module One
  def a(*)
    puts 'One...'
    super
  end
end

module Two
  def a(*)
    puts 'Two...'
    super
  end
end

class Test
  def a(*args)
    puts 'Zero'
  end
end

Test.new.a
#Zero

Test.class_eval do
  prepend One
end

Test.new.a
#One...
#Zero

Test.class_eval do
  prepend Two
end

Test.new.a
#Two...
#One...
#Zero