diff --git a/Bitly.cabal b/Bitly.cabal
--- a/Bitly.cabal
+++ b/Bitly.cabal
@@ -1,5 +1,5 @@
 Name:          Bitly
-Version:       0.0.1
+Version:       0.0.2
 Cabal-version: >= 1.2
 Build-type:    Simple
 
@@ -17,16 +17,24 @@
   .
   API key is required. Please find yours at <http://bit.ly/account/>.
   .
-  An optional command line utility is provided (use `-f buildCLI` to build it).
+  Configuration file (`~/.bitly`) format:
+  .
+  > login = your_bit.ly_login
+  > apikey = your_API_key
+  .
+  Examples (command line utility):
+  .
+  > $ echo "Text with an URL: http://example.com/" | bitly
+  > Text with an URL: http://bit.ly/2eSq1z
+  > $ bitly shorten http://example.com
+  > http://bit.ly/2eSq1z
+  > $ bitly expand http://bit.ly/2eSq1z
+  > http://example.com/
 
 Homepage:      http://bitbucket.org/jetxee/hs-bitly/
 Bug-reports:   http://bitbucket.org/jetxee/hs-bitly/issues/
 Tested-with:   GHC == 6.10
 
-Flag buildCLI
-  Description: Build a command line tool to access bit.ly service.
-  Default:     False
-
 Library
   Build-depends:
                  base >= 3 && < 5
@@ -36,9 +44,8 @@
 
 Executable bitly
   Main-is:     bitly.hs
-  if !flag(buildCLI)
-    Buildable: False
   Build-depends:
                  filepath
                , directory
+               , regexpr
 
diff --git a/Network/Bitly.hs b/Network/Bitly.hs
--- a/Network/Bitly.hs
+++ b/Network/Bitly.hs
@@ -42,8 +42,15 @@
        -> IO Result -- ^ Either error or long source URL
 expand acc url = request acc "expand" [("shortUrl", url)]
                              [ "bitly", "results", code, "longUrl" ]
-  where code = reverse . takeWhile (/= '/') . reverse $ url -- ending of the URL
+  where
+    ending d = foldr (\x xs -> if d `elem` xs then xs else x:xs) ""
+    code = dropHeadIf (== '/') $ ending '/' url
 
+dropHeadIf :: (a -> Bool) -> [a] -> [a]
+dropHeadIf _ [] = []
+dropHeadIf p all@(x:xs)
+  | p x        = xs
+  | otherwise  = all
 
 -- | Internal function to accomodate all types of requests
 request :: Account    -- ^ Account to use
@@ -52,9 +59,9 @@
         -> [String]   -- ^ Path to the node with the result in the XML response
         -> IO Result
 request acc path params xmlpath = do
-  let baseURL = (server acc) ++ "/" ++ path
+  let baseURL = server acc ++ "/" ++ path
   let params' = loginParams ++ params :: [ (String, String) ]
-  let reqURL  = baseURL ++ "?" ++ (urlEncodeVars params')
+  let reqURL  = baseURL ++ "?" ++ urlEncodeVars params'
   let req     = getRequest reqURL :: Request String
   resp <- simpleHTTP req
   case resp of
@@ -78,15 +85,15 @@
   let cs = tag "bitly" /> tag "statusCode" /> txt $ root
   case cs of
     [] -> Left "No statusCode in response"
-    (CString _ code:_) -> do
-          if (code /= "OK")
+    (CString _ code:_) ->
+          if code /= "OK"
             then
               let err = concatMap (render . content) $
                         tag "bitly" /> tag "errorMessage" /> txt $ root
               in  Left $ "Bit.ly error: " ++ err
             else
               let url' = concatMap (render . content) $
-                         (foldr (/>) txt $ map tag xmlpath ) $ root
+                         foldr (/>) txt (map tag xmlpath) root
               in  if null url'
                     then Left "Result not found"
                     else Right url'
diff --git a/bitly.hs b/bitly.hs
--- a/bitly.hs
+++ b/bitly.hs
@@ -4,12 +4,13 @@
 
 import Control.Applicative ((<$>))
 import Data.Char (isSpace)
-import Data.Maybe (fromJust, isJust, isNothing)
+import Data.Maybe (fromJust, fromMaybe, isJust, isNothing)
 import System.Directory (getHomeDirectory)
 import System.Environment (getArgs)
 import System.Exit (exitFailure, exitSuccess)
 import System.FilePath (makeValid, combine)
 import System.IO (hPutStrLn, stderr)
+import Text.RegexPR
 
 confFileName :: IO String
 confFileName = makeValid <$> flip combine ".bitly" <$> getHomeDirectory
@@ -32,15 +33,34 @@
 
 errorExit s = hPutStrLn stderr s >> exitFailure
 
-printModifiedUrl :: (String -> IO Result) -> String -> IO ()
-printModifiedUrl op url = do
+modifyUrl :: (String -> IO Result) -> String -> IO String
+modifyUrl op url = do
   r <- op url
   case r of
-    Left err -> errorExit err
-    Right url' -> putStrLn url'
+    -- don't replace URL on error
+    Left _ -> return url
+    Right url' -> return url'
 
-usage = "Usage: bitly ( help | [shorten] [url ...] | expand [url ...] )\n\n\
-\Configuration file format:\n\
+urlRE = "(http|ftp|https)://\\w+(\\.\\w+)(:[0-9]+)?(/\\S+)?/?"
+
+passThrough :: (String -> IO Result) -> String -> IO String
+passThrough op txt =
+  let m = matchRegexPR urlRE txt
+  in case m of
+    Nothing -> return txt
+    Just ((url,(b,a)),_) -> do
+      url' <- modifyUrl op url
+      return . ((b ++ url') ++) =<< passThrough op a
+
+-- process all given urls or read stdin and pass it through
+runOp :: (String -> IO Result) -> [String] -> IO ()
+runOp op [] = putStr =<< passThrough op =<< getContents
+runOp op urls = mapM_ putStrLn =<< mapM (modifyUrl op) urls
+
+usage = "Usage: bitly [ help | [shorten] [url ...] | expand [url ...] ]\n\n\
+\If no url is given, bitly acts as a filter and replaces all found URLs.\n\
+\Bitly shortens URLs by default.\n\n\
+\Configuration file format (~/.bitly):\n\
 \  login = your_bit.ly_login\n\
 \  apikey = your_API_key"
 
@@ -57,7 +77,7 @@
       errorExit $ "Configuration file is incomplete or not found (" ++ f ++ ")"
     Just acc ->
       case args of
-        ("expand":urls) -> printModifiedUrl (expand acc) `mapM_` urls
-        ("shorten":urls) -> printModifiedUrl (shorten acc) `mapM_` urls
-        _  -> printModifiedUrl (shorten acc) `mapM_` args -- shorten by default
+        ("expand":urls) -> runOp (expand acc) urls
+        ("shorten":urls) -> runOp (shorten acc) urls
+        _  -> runOp (shorten acc) args -- shorten by default