diff --git a/Nemesis b/Nemesis
--- a/Nemesis
+++ b/Nemesis
@@ -15,9 +15,6 @@
     sh "cabal configure"
     sh "cabal sdist"
 
-  desc "start console"
-  task "i" (sh "ghci -isrc src/Test.hs")
-
   desc "put all .hs files in manifest"
   task "manifest" $ do
     sh "find . | grep 'hs$' > manifest"
@@ -31,10 +28,12 @@
 
   ghci "template" "Network/Loli/Template"
   ghci "ipaste" "Test/LoliPaste"
+  ghci "i" "Test/Test"
   
   bin "test" "Test/Test"
   bin "paste" "Test/LoliPaste"
-  bin "myloli" "Test/myloli"
+  bin "myapp" "Test/myapp"
+  bin "debug" "Debug/Debug"
   
   
   -- test
diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,14 +1,26 @@
+2009.7.2
+--------
+
+### Features
+
+* before / after filter
+* On the fly router switcher
+
+### Fix
+
+* safari display weird header
+
 2009.6.29
 ---------
 
-### Feature
+### Features
 
 * Initial hackage release
 
 2009.6.27
 ---------
 
-### Feature
+### Features
 
 * add template
 * add local binding
@@ -17,7 +29,7 @@
 2009.6.26
 ---------
 
-### Feature
+### Features
 
 * add route
 
diff --git a/known-issues.md b/known-issues.md
--- a/known-issues.md
+++ b/known-issues.md
@@ -1,2 +1,1 @@
-* safari display weird header info
 * unknown server socket error in LoliPaste.hs, it has something to do with unicode convertion, i.e. changing ls form MPSUTF8 to ls in MPS fix the problem, but encoding stays in utf-8 instead of plain unicode chars
diff --git a/loli.cabal b/loli.cabal
--- a/loli.cabal
+++ b/loli.cabal
@@ -1,5 +1,5 @@
 Name:                 loli
-Version:              2009.6.29
+Version:              2009.7.2
 Build-type:           Simple
 Synopsis:             A minimum web dev DSL in Haskell
 Description:
@@ -25,6 +25,7 @@
                       Network.Loli.Config
                       Network.Loli.DSL
                       Network.Loli.Engine
+                      Network.Loli.Middleware.IOConfig
                       Network.Loli.Middleware.LoliRouter
                       Network.Loli.Middleware.UserMime
                       Network.Loli.Template
diff --git a/readme.md b/readme.md
--- a/readme.md
+++ b/readme.md
@@ -6,7 +6,7 @@
 
 First app
 
-    -- myloli.hs
+    -- myapp.hs
     
     import Network.Loli
     import Hack.Handler.Happstack
@@ -19,15 +19,15 @@
     cabal install loli
     cabal install hack-handler-happstack
     
-    ghc --make myloli.hs
-    ./myloli
+    ghc --make myapp.hs
+    ./myapp
 
 check: <http://localhost:3000>
 
 
 ## Routes
 
-### Verb
+### Verbs
 
     get "/" $ do
       -- something for a get request
@@ -40,6 +40,7 @@
     
     delete "/" $ do
       -- ..
+
 ### Captures
 
     get "/say/:user/:message" $ do
@@ -51,7 +52,7 @@
 
 ## Static
 
-    -- public serve, only allows /src
+    -- public serve, only allows `./src`
     public (Just ".") ["/src"]
 
 ## Views root
@@ -65,7 +66,6 @@
 
     import Network.Loli.Template.TextTemplate
     
-    -- template
     get "/hi/:user" $ output (text_template "hello.html")
     
     -- in hello.html
@@ -137,6 +137,22 @@
     -- treat .hs extension as text/plain
     mime "hs" "text/plain"
 
+## Filters
+
+    -- before takes a function of type (Env -> IO Env)
+    before $ \e -> do
+      putStrLn "before called"
+      return e
+    
+    -- after takes that of type (Response -> IO Response)
+    after return
+
+## On the fly router switcher
+
+The router can be switched at any time, it will effect any route path that follows.
+    
+    router loli_router
+
 ## Hack integration
 
 ### Use hack middleware
@@ -155,4 +171,8 @@
 
 ## Note
 
-If you see this, use the git version!
+use the git version ...
+
+## Reference
+
+* loli is inspired by [Rack](http://rack.rubyforge.org), [Rails](http://rubyonrails.org), [Ramaze](http://ramaze.net), [Happstack](http://happstack.com/) and [Sinatra](http://www.sinatrarb.com/).
diff --git a/src/Network/Loli/Config.hs b/src/Network/Loli/Config.hs
--- a/src/Network/Loli/Config.hs
+++ b/src/Network/Loli/Config.hs
@@ -18,32 +18,28 @@
   where
     set_view_root env =
       let hack_headers = env.hackHeaders
-          pre_config = [(loli_config ++ loli_views, loli_default_views)]
+          pre_config   = [(loli_config ++ loli_views, loli_default_views)]
       in
       env {hackHeaders = hack_headers ++ pre_config}
     default_content_type :: String
     default_content_type = "text/plain; charset=UTF-8"
-    
-loli_captures :: String
-loli_captures = "loli-captures-"
 
-loli_locals :: String
-loli_locals = "loli-locals-"
 
-loli_partials :: String
-loli_partials = "loli-partials-"
 
-loli_config :: String
-loli_config = "loli-config-"
-
-loli_layout :: String
-loli_layout = "layout"
-
-loli_views :: String
-loli_views = "views"
-
-loli_default_views :: String
-loli_default_views = "views"
-
+loli_captures       :: String
+loli_locals         :: String
+loli_partials       :: String
+loli_config         :: String
+loli_layout         :: String
+loli_views          :: String
+loli_default_views  :: String
 loli_layout_content :: String
+
+loli_captures       = "loli-captures-"
+loli_locals         = "loli-locals-"
+loli_partials       = "loli-partials-"
+loli_config         = "loli-config-"
+loli_layout         = "layout"
+loli_views          = "views"
+loli_default_views  = "views"
 loli_layout_content = "content"
diff --git a/src/Network/Loli/DSL.hs b/src/Network/Loli/DSL.hs
--- a/src/Network/Loli/DSL.hs
+++ b/src/Network/Loli/DSL.hs
@@ -3,11 +3,13 @@
 import Control.Monad.Reader
 import Control.Monad.State
 import Hack
+import Hack.Contrib.Middleware.Censor
 import Hack.Contrib.Middleware.Config
 import Hack.Contrib.Middleware.Static
 import MPS
 import Network.Loli.Config
 import Network.Loli.Engine
+import Network.Loli.Middleware.IOConfig
 import Network.Loli.Type
 import Network.Loli.Utils
 import Prelude hiding ((.), (>), (^))
@@ -24,14 +26,24 @@
 views :: String -> Unit
 views x = middleware $ config (set_namespace loli_config loli_views x)
 
-get, put, delete, post :: String -> AppUnit -> Unit
-get    = route GET
-put    = route PUT
-delete = route DELETE
-post   = route POST
+router :: Router -> Unit
+router = set_router > update
 
+get, put, post, delete :: String -> AppUnit -> Unit
+get    = add_route GET
+put    = add_route PUT
+post   = add_route POST
+delete = add_route DELETE
+
+
 middleware :: Middleware -> Unit
-middleware x = add_middleware x .update
+middleware = add_middleware > update
+
+before :: (Env -> IO Env) -> Unit
+before = ioconfig > middleware
+
+after :: (Response -> IO Response) -> Unit
+after = censor > middleware
 
 mime :: String -> String -> Unit
 mime k v = add_mime k v .update
diff --git a/src/Network/Loli/Engine.hs b/src/Network/Loli/Engine.hs
--- a/src/Network/Loli/Engine.hs
+++ b/src/Network/Loli/Engine.hs
@@ -17,28 +17,34 @@
 import Prelude hiding ((.), (/), (>), (^))
 
 run_app :: AppUnit -> Application
-run_app unit = \env -> runReaderT unit env .flip execStateT def
+run_app unit = \env -> runReaderT unit env .flip execStateT def {status = 200}
 
 loli :: Unit -> Application
 loli unit = run unit (not_found empty_app)
   where
+    run_route x = (x.router) loli_captures run_app (x.route_path)
+    
     run :: Unit -> Middleware
     run unit' = 
-      let loli_state  = execState unit' def
-          paths       = loli_state.routes
-          
-          loli_app    = loli_router loli_captures run_app paths 
-          mime_filter = user_mime (loli_state.mimes)
-          stack       = loli_state.middlewares.use
-          pre         = pre_installed_middlewares.use
+      let loli_state    = execState unit' def
+          route_configs = loli_state.routes
+          route         = route_configs.map run_route .use
+          mime_filter   = user_mime (loli_state.mimes)
+          stack         = loli_state.middlewares.use
+          pre           = pre_installed_middlewares.use
       in
-      use [pre, mime_filter, stack, loli_app]
+      use [pre, mime_filter, stack, route]
 
-add_route :: RoutePath -> Loli -> Loli
-add_route r s = let xs = s.routes in s {routes = xs.insert_last r}
+add_route_config :: RouteConfig -> Loli -> Loli
+add_route_config r s = let xs = s.routes in s {routes = xs.insert_last r}
 
-route :: RequestMethod -> String -> AppUnit -> Unit
-route r s u = update $ add_route (r, s, u)
+add_route :: RequestMethod -> String -> AppUnit -> Unit
+add_route r s u = do
+  c <- get ^ current_router
+  update $ add_route_config RouteConfig { route_path = (r, s, u), router = c }
+
+set_router :: Router -> Loli -> Loli
+set_router r x = x { current_router = r }
 
 add_middleware :: Middleware -> Loli -> Loli
 add_middleware x s = 
diff --git a/src/Network/Loli/Middleware/IOConfig.hs b/src/Network/Loli/Middleware/IOConfig.hs
new file mode 100644
--- /dev/null
+++ b/src/Network/Loli/Middleware/IOConfig.hs
@@ -0,0 +1,6 @@
+module Network.Loli.Middleware.IOConfig (ioconfig) where
+
+import Hack
+
+ioconfig :: (Env -> IO Env) -> Middleware
+ioconfig before app = \env -> before env >>= app
diff --git a/src/Network/Loli/Middleware/LoliRouter.hs b/src/Network/Loli/Middleware/LoliRouter.hs
--- a/src/Network/Loli/Middleware/LoliRouter.hs
+++ b/src/Network/Loli/Middleware/LoliRouter.hs
@@ -1,6 +1,5 @@
 module Network.Loli.Middleware.LoliRouter (loli_router) where
 
-import Data.List (find)
 import Data.Maybe
 import Hack
 import Hack.Contrib.Utils
@@ -9,22 +8,24 @@
 import Prelude hiding ((.), (>), (/))
 
 
-type RoutePathT a   = (RequestMethod, String, a)
-type Assoc          = [(String, String)]
+type RoutePathT a = (RequestMethod, String, a)
+type Assoc        = [(String, String)]
 
-loli_router :: String -> (a -> Application) -> [RoutePathT a] -> Middleware
-loli_router prefix runner h app' = \env'' ->
-  let path             = env''.path_info
-      script           = env''.script_name
-      mod_env location = env'' 
+
+loli_router :: String -> (a -> Application) -> RoutePathT a -> Middleware
+loli_router prefix runner route_path app' = \env ->
+  let path             = env.path_info
+      script           = env.script_name
+      mod_env location = env 
         { scriptName  = script ++ location
         , pathInfo    = path.drop (location.length)
         }
   in
-  case h.find (match_route env'') of
-    Nothing -> app' env''
-    Just (_, template, app_state) -> do
-      let (location, params) = parse_params template path .fromJust
+  if route_path.match_route env.not
+    then app' env
+    else do
+      let (_, template, app_state) = route_path
+          (location, params) = parse_params template path .fromJust
       runner app_state (mod_env location .merge_captured params)
   where
     match_route env' (method, template, _) = 
@@ -35,13 +36,14 @@
 
 
 parse_params :: String -> String -> Maybe (String, Assoc)
-parse_params "" ""   = Just ("", [])
-parse_params "" _    = Nothing
+parse_params "" ""  = Just ("", [])
+parse_params "" _   = Nothing
 parse_params "/" "" = Nothing
-parse_params "/" _ = Just ("/", [])
-parse_params t s =
+parse_params "/" _  = Just ("/", [])
+
+parse_params t s = 
   let template_tokens = t.split "/"
-      url_tokens = s.split "/"
+      url_tokens      = s.split "/"
   in
   if url_tokens.length < template_tokens.length
     then Nothing
@@ -50,9 +52,10 @@
       in
       if rs.all isJust
         then 
-          let location = "/" / url_tokens.take (template_tokens.length).join "/"
+          let token_length = template_tokens.length
+              location     = "/" / url_tokens.take token_length .join "/"
           in
-          Just $ (location, rs.map fromJust.filter isJust.map fromJust)
+          Just $ (location, rs.catMaybes.catMaybes)
         else Nothing
   
   where
@@ -64,8 +67,8 @@
 -- copy from loli utils
 put_namespace :: String -> Assoc -> Env -> Env
 put_namespace x xs env = 
-  let adds = xs.map_fst (x ++)
-      new_headers = adds.map fst
+  let adds             = xs.map_fst (x ++)
+      new_headers      = adds.map fst
       new_hack_headers = 
         env.custom.reject (fst > belongs_to new_headers) ++ adds
   in
diff --git a/src/Network/Loli/Template.hs b/src/Network/Loli/Template.hs
--- a/src/Network/Loli/Template.hs
+++ b/src/Network/Loli/Template.hs
@@ -35,9 +35,9 @@
 template_locals :: AppUnitT Context
 template_locals = do
   c <- captures
-  b <- locals
+  l <- locals
   p <- partial_locals
-  return (c ++ b ++ p)
+  return (c ++ l ++ p)
 
 render :: (Template a) => a -> AppUnitT String
 render x = do
diff --git a/src/Network/Loli/Template/TextTemplate.hs b/src/Network/Loli/Template/TextTemplate.hs
--- a/src/Network/Loli/Template/TextTemplate.hs
+++ b/src/Network/Loli/Template/TextTemplate.hs
@@ -8,8 +8,8 @@
 import Text.Template hiding (Context, Template, template)
 import qualified Text.Template as T
 
-render_TextTemplate :: String -> Context -> IO String
-render_TextTemplate x c = 
+render_text_template :: String -> Context -> IO String
+render_text_template x c = 
   readTemplate (x.u2b) ^ flip T.render (create_context c) ^ toString
   where
     create_context = map (fromString *** fromString) > to_h
@@ -17,7 +17,7 @@
 data TextTemplate = TextTemplate String
 
 instance Template TextTemplate where
-  interpolate (TextTemplate x) r = render_TextTemplate (r / x)
+  interpolate (TextTemplate x) r = render_text_template (r / x)
 
 text_template :: String -> TextTemplate
 text_template = TextTemplate
diff --git a/src/Network/Loli/Type.hs b/src/Network/Loli/Type.hs
--- a/src/Network/Loli/Type.hs
+++ b/src/Network/Loli/Type.hs
@@ -5,28 +5,37 @@
 import Data.Default
 import Hack
 import Hack.Contrib.Utils
+import Network.Loli.Middleware.LoliRouter
 
-type RoutePathT a   = (RequestMethod, String, a)
-type RoutePath      = RoutePathT AppUnit
-type EnvFilter      = Env -> Env
-type ResponseFilter = Response -> Response
-type Assoc          = [(String, String)]
-type AppState       = Response
-type AppReader      = Env
+type RoutePathT a = (RequestMethod, String, a)
+type RoutePath    = RoutePathT AppUnit
+type AppReader    = Env
+type AppState     = Response
+type AppUnitT     = ReaderT AppReader (StateT AppState IO)
+type AppUnit      = AppUnitT ()
+type Assoc        = [(String, String)]
+type Context      = Assoc
 
-type AppUnitT       = ReaderT AppReader (StateT AppState IO)
-type AppUnit        = AppUnitT ()
-type Context        = Assoc
+type RouterT a = String -> (a -> Application) -> RoutePathT a -> Middleware
+type Router    = RouterT AppUnit
 
+data RouteConfig = RouteConfig
+  {
+    route_path :: RoutePath
+  , router     :: Router
+  }
+
 data Loli = Loli
   {
-    routes :: [RoutePath]
-  , middlewares :: [Middleware]
-  , mimes :: Assoc
+    current_router  :: Router
+  , routes          :: [RouteConfig]
+  , middlewares     :: [Middleware]
+  , mimes           :: Assoc
   }
 
+
 instance Default Loli where
-  def = Loli def [dummy_middleware] def
+  def = Loli loli_router def [dummy_middleware] def
 
 
 type UnitT a = State Loli a
diff --git a/src/Network/Loli/Utils.hs b/src/Network/Loli/Utils.hs
--- a/src/Network/Loli/Utils.hs
+++ b/src/Network/Loli/Utils.hs
@@ -15,8 +15,8 @@
 
 put_namespace :: String -> [(String, String)] -> Env -> Env
 put_namespace x xs env = 
-  let adds = xs.map_fst (x ++)
-      new_headers = adds.map fst
+  let adds             = xs.map_fst (x ++)
+      new_headers      = adds.map fst
       new_hack_headers = 
         env.custom.reject (fst > belongs_to new_headers) ++ adds
   in
diff --git a/src/Test/Test.hs b/src/Test/Test.hs
--- a/src/Test/Test.hs
+++ b/src/Test/Test.hs
@@ -8,6 +8,7 @@
 import Network.Loli.Template.ConstTemplate (const_template)
 import Network.Loli.Template.TextTemplate
 import Network.Loli.Utils
+import Network.Loli.Middleware.LoliRouter
 import Data.Maybe
 import MPS ((^))
 import Prelude hiding ((^))
@@ -15,14 +16,21 @@
 
 -- default on port 3000
 
+main :: IO ()
 main = run . loli $ do
   
     middleware lambda
     middleware show_status
+    
+    before return
+    after return
 
     get "/bench"     $ do
       name <- ask ^ params ^ lookup "name" ^ fromMaybe "nobody"
       html ("<h1>" ++ name ++ "</h1>")
+
+    -- on the fly router switcher
+    router loli_router
 
     -- simple
     get "/hello"    (text "hello world")