split.hs

startWith :: (Eq a) => [a] -> [a] -> Maybe [a]
startWith [] ys = Just ys
startWith xs [] = Nothing
startWith (x:xs) (y:ys)
  | x == y = startWith xs ys
  | otherwise = Nothing

split :: (Eq a) => [a] -> [a] -> [[a]]
split []  lst = [lst]
split sep lst = split' [] lst
  where split' acc [] = [acc]
        split' acc (x:xs) =
          case startWith sep (x:xs) of
            Just ys -> [acc] ++ split' [] ys
            Nothing -> split' (acc ++ [x]) xs