This gist will lich all your free time, so be warned!

ruby 1.8 vs 1.9 alias_method + extend.rb

class Q
  def add
    puts "added to Q"
  end
end

queue = Q.new

notifier = Module.new do
  def add(*args)
    super
    puts "i am from notifier!"
  end
  alias_method :push, :add
  alias_method :<<,   :add
end
queue.send :extend, notifier

# Ok, lets try:
queue.add

# Ruby 1.9
# added to Q
# i am from notifier!

# Ruby 1.8
# added to Q
# i am from notifier!


# what about our aliases?
queue.push

# Ruby 1.9
# added to Q
# i am from notifier!


# Ruby 1.8
# test.rb:11:in `push': super: no superclass method `add' for #<Q:0x1dbf0f0> (NoMethodError)
# from test.rb:19

# WTF?!