Based on: http://www.youtube.com/watch?v=dkZFtimgAcM

monard.rb

class Monad
  def self.unit(value)
    monad = new
    monad.define_singleton_method(:bind) { |func, *args| func.call(*([value] + args)) }

    monad
  end

  def lift(name, func, *args)
    define_singleton_method(name) { Monad.unit(bind(func, args)) }
    self
  end
end

identity = Monad.unit("Hello World")
identity.bind(lambda { |arg| puts arg })