ISA-like URI proxy

As we are preparing to deploy LTM/APM in our environment, and moving things from our ISA server to the F5 appliance, I'm running into a difficulty trying to get something to work.

Currently, within the ISA, we have a site set up to user a specific URI to determine the route. For example, http://example.com/App1 will connect on the back end to the server app1.domain.local. With the ISA, the /App1/ seems to persist as expected throughout the session, even though on the back end I know that the connection would be going to app1.domain.local/{RestOfUri} rather than app1.domain.local/App1/{RestOfUri}.

What I'm trying to do with the F5 is get that same type of experience by using part of the URI as a deciding factor for which pool to send the connection to. The problem is that I can do that the first time and change the HTTP::path to remove the /App1 from the url so it will hit the back end server properly, but once the response comes back, some of its links (e.g. "/{link}") will now be associated with the host root rather than root plus uri prefix (e.g. example.com/{link} vs example.com/App1/{link}). In this instance, we are not using the APM because one of the sites I'm trying to get working is part of our login process, and is non-authenticated.

I've tried a number of different ideas through iRules, but I can't seem to find a way that will work consistently and give me the same experience I've had with the ISA.

Any help would be greatly appreciated. Thanks, Michael