Frank is a Sinatra-inspired DSL (see http://www.sinatrarb.com) for creating routes. It is composable with all ToApplication types, but is designed to be used with Controllers. Each verb (get, post, put, etc') takes a URL pattern of the form "/dir/:paramname/dir" (see routePattern for details) and a ToApplication:

  main :: IO ()
  main = run 3000 $ controllerApp () $ do
    get "/" $ do
      req <- request
      respond $ okHtml $ fromString $
        "Welcome Home " ++ (show $ serverName req)
    get "/user/:id" $ do
      userId <- queryParam "id" >>= fromMaybe ""
      respond $ ok "text/json" $ fromString $
        "{\"myid\": " ++ (show userId) ++ "}"
    put "/user/:id" $ do
      ...