It's not quite defining a monad, but it's very close. The example given in the article is: data_source.person(id) do |person| person.phone_number =

It's not quite defining a monad, but it's very close. The example given in the article is: data_source.person(id) do |person| person.phone_number = phone_number data_source.update_person person end You can abstract this pattern a little by putting it in a function: def maybe_bind(x, &blk) if !x.nil? blk.call(x) else nil end end Now consider the type of this function: nil or X, (X -> nil or Y) -> nil or Y A monad is any type for which you can define bind and return. They have the Haskell types: bind :: m a -> (a -> m b) -> m b return :: a -> m a "maybe_bind" is very similar to "bind"; just replace "m" with "nil or" and uncurry. "return" is trivial to implement.