9-10  Keep track of the original SCRIPT_NAME/PATH_INFO
   19  Send the request to the application
11-18  Capture the status and the headers
   14  Are we interested in filtering this?
         No:
   15      Pass response up unmodified
         Otherwise:
   17      Capture the status and headers
   20  If the status and headers were not captured:
   21    Pass the response body up unmodified
24-25  Collect all the response body
27-28  Call app_iter.close() if possible    
30-31  Filter that output and send that filtered response
32-33  Generate the response

   41  HTMLFilter:
43-49  We are interested in all OK responses that are text/html