Needing the `Either a` monad in Ruby

either.hs

loadStuff :: Map -> Either String (ThingOne, ThingTwo)
loadStuff params = do
  thingOne <- loadThingOne params
  thingTwo <- loadThingTwo params thingOne
  checkSomething thingTwo
  return (thingOne, thingTwo)

either.rb

def load_stuff(params)
  thing_one, error = load_thing_one(params)
  return [nil, nil, error] unless thing_one

  thing_two, error = load_thing_two(params, thing_one)
  return [nil, nil, error] unless thing_two

  error = check_something(thing_two)
  return [nil, nil, error] if error

  [thing_one, thing_two, nil]
end

You might find this Either monad useful https://github.com/pzol/monadic#either