Help with removing certain header information from URI

There's no need for a temporary variable. One thing to note about iRules in 9.x is that they're a full-blown programming language, and the "pool" command is simply that - a command. There's no implied termination of evaluation upon calling it.

That said, the following should work. Note that it rewrites the URI on its way to the server. The client will not see anything different in its browser bar. If you need the client to send a request for a new URI altogether, consider using the HTTP::redirect command instead of rewriting the URI on the fly.

 
 rule adsif5 { 
    when HTTP_REQUEST { 
         if {[HTTP::uri] contains "/customer1"} { 
             pool customer1 
         } elseif {[HTTP::uri] contains "/customer2"} { 
             pool customer2 
         } else { 
             pool Supporthomepage 
             return 
         } 
         if {[HTTP::uri] starts_with "/webcentral"} { 
             HTTP::uri "/archibus" 
         } 
     } 
 }