iRule inspecting body response

I think you can do something like:

STREAM::disable
STREAM::expression "this.location.replace("https://"
STREAM::enable

Then use the STREAM_MATCHED event:

when STREAM_MATCHED {
  log local0. "Stream found."
  }

You may need to play with it some, I can't remember exactly how to do this, but it can be done. You can search with stream and then NOT replace.