Adding class methods from a module, that are added to the class hierarchy (so you can use super, unlike with Module#extend)

gistfile1.rb

module Foo
  def find(*)
    "Foo#find"
  end
end

class Blah
  class << self
    include Foo
  end

  def self.find(*)
    "Blah.find -- #{super}"
  end
end

Blah.find #=> "Blah.find -- Foo#find"