Python like string split in Haskell

Following function split a string into a list of strings at a given string. For example split "dilawar raw war" "aw" returns ["dil", "ar r" " war"]

split :: String -> String -> [String]
split str pat = helper str pat [] [] where
    helper :: String -> String -> String -> String -> [String]
    helper [] ys n m = [n] ++ []
    helper xs [] n m = [n] ++ (split xs pat)
    helper (x:xs) (y:ys) n m
        | x /= y = helper (xs) pat ((n++m)++[x]) m
        | otherwise = helper xs ys n (m++[y])