Rewrite host and URI, then redirect

So my requirements have changed a bit. I have the code below working. However what we now need to do is NOT send a redirect to the client and instead rewrite the uri portion of the request and send that to an existing server pool.

 

 

I'm confused about how to not pass the cached uri and instead pass what I've rewritten to the pool members. The host value should remain unchanged now.

 

 

  
 when HTTP_REQUEST {   
      switch [string tolower [HTTP::host]] {   
         "app.domain.com" {   
            set host "www.google.com" 
            set uri [string map -nocase {"/path_to_replace" "/new_path" "index.jsp" "index.asp"} [HTTP::uri]] 
            HTTP::redirect http://$host$uri 
         }   
      }   
   } 
 

 

 

 

I tried setting HTTP::uri and then using 'pool pool_name', but the original uri value seems to be passed, not what I've rewritten.