gistfile1.rb

module MyModule
  def self.extend_object(obj)
    puts "Hello from #{self}"
    super # important
  end

  def self.hello
    puts "Hello from #{self}"
  end
end

pry(main)> (myextendedstring = "blah").extend(MyModule)
#=> Hello from MyModule
#=> "blah"
pry(main)> s.hello
#=> "Hello from blah"