anchor.diff:  [source, haskell]
   ----
   {-# LANGUAGE OverloadedStrings #-}
  -import Network.Wai
  -import Network.Wai.Handler.Warp
  -import Network.HTTP.Types
  -import Text.Blaze.Html5
  -import qualified Text.Blaze.Html5 as H
  -import Text.Blaze.Html.Renderer.Utf8
  +import           Network.HTTP.Types            (status200)
  +import           Network.Wai                   (Application, responseBuilder)
  +import           Network.Wai.Handler.Warp      (run)
  +import           Text.Blaze.Html.Renderer.Utf8 (renderHtmlBuilder)
  +import           Text.Blaze.Html5              (Html, docTypeHtml)
  +import qualified Text.Blaze.Html5              as H
   
   main :: IO ()
   main = run 3000 app
   
   app :: Application
  -app req = return $ responseBuilder
  +app _req = return $ responseBuilder
       status200
       [("Content-Type", "text/html")] -- yay!
       (renderHtmlBuilder myPage)
  
positive.code: [source, haskell]
  ----
  {-# LANGUAGE OverloadedStrings #-}
  import Network.Wai
  import Network.Wai.Handler.Warp
  import Network.HTTP.Types
  
  main :: IO ()
  main = run 3000 app
  
negative.code: [source, haskell]
  ----
  {-# LANGUAGE OverloadedStrings #-}
  import           Network.HTTP.Types       (status200)
  import           Network.Wai              (Application, pathInfo, responseLBS)
  import           Network.Wai.Handler.Warp (run)
  
  main :: IO ()
  main = run 3000 app
  