View difference between Paste ID: GAaZnDch and pCPZRmgX

 import System.IO
 import System.Environment
 import Data.List
 import Data.Maybe
-replace :: String -> String -> String -> String
+
 replace _ _ [] = []
 replace src dst s@(x:xs) = case stripPrefix src s of
                                 Just a -> dst ++ replace src dst a
                                 Nothing -> (x:replace src dst xs)
 
 split _ [] = [[]]
 split c xs = case span (/= c) xs of
                 (f, []) -> [f]
                 (f, r)  -> (f:split c (tail r))
 
 data Rule = Rule {from, to :: String, terminal :: Bool}
-    deriving Show
+
 readRule (x:y:z) = Rule {from = x, to = y, terminal = not $ null z}
 readRule _ = error "Wrong rule syntax"
 
-applyRule rule = replace (from rule) (to rule)
+applyRule rules str = do s <- str
                          rule <- find ((`isInfixOf` s) . from) rules
                          return $ replace (from rule) (to rule) s
 
-          let startStr = args !! 1
+
-          putStrLn $ "0: " ++ startStr
+
-          run 1 rules (args !! 1)
+          mapM putStrLn $ zipWith (\step str -> show step ++ ": " ++ fromJust str) [0..]
-       where run step rules str = putStr (show step ++ ": ") >>
+                                  (takeWhile isJust . iterate (applyRule rules) . Just $ args !! 1)