myUnlines :: [String] -> String
myUnlines = foldl' step ""
  where
    step :: String -> String -> String
    step r l = r ++ l ++ "\n"
myUnlines :: [String] -> String
myUnlines = foldl' step ""
  where
    step :: String -> String -> String
    step r l = r ++ l ++ "\n"
myUnlines = foldl' step ""
  where
    step :: String -> String -> String
    step r l = r ++ l ++ "\n"