Haskell pattern question

test.hs

-- In `f` we want to keep piping (part of) the result of one function into
-- another, and stop as soon as something fails
f :: [A] -> Either String (B, [A])
f xs =
  case f1 xs of
    Left s -> Left s
    Right (res1, xs') ->
      case f2 xs' of
        Left s -> Left s
        Right (res2, xs'') ->
          case f3 xs'' of
            Left s -> Left s
            Right (res3, xs''') ->
              Right (B res1 res2 res3, xs''')


-- In `g` we want to keep trying different functions with the same input
-- until something succeeds, and then stop
g :: [A] -> Either String (B, [A])
g xs =
  case g1 xs of
    Right (res1, xs') -> Right (res1, xs')
    Left s ->
      case g2 xs of
        Right (res2, xs') -> Right (res2, xs')
        Left s ->
          case g3 xs of
            Right (res3, xs') -> Right (res3, xs')
            Left s -> Left s