Really appreciate your detailed reply.
By the way, it came to as a surprise that 540 can support 9.x version. 6 months back a call to F5 gave us a different answer that it just cant run on 540. Can you pl. confirm as you are F5 person pl?
The reason I want to use it this way is as follows...
We have 12 servers in web farm as 3 groups of 4 servers each catering for different set of business apps. All servers are always live and get tons of hit everyday. However at the same time we as SA need to point browsers to a perticular server to test apps on it, using test urls.
This is achieved by setting up separate VIPs for live (production) urls and for test urls. Based on requested http_uri cookie set, the irules points traffic to either perticular box in production farm or to the load balanced production farm.
We have 6 lines of if-endif in production irules and adding one or more to it causes performance impact. I can add one at the most, hence thought of adding that one to check http_uri and cookie as mentioend above and branching out to the pool which contains IPs of servers I wish to access, based on cookie. mapclass2node can help me there, however situation demands that it is not just checking cookie, but couple of more things in http_uri. Thats why I need to do complex settings in node expression. Since this expression will only be accessible to urls that are used to point to perticular server, it wont put perf. impact on live production rules, and still get my job done.
Sorry it was bit complex to explain here. If you still need mock-up of prod I will provide it to you. Thx for help again.