I have a server (S-1) with HAProxy and a number of residential proxies (PR-s) as login-passwords-port. There're multiple users who will connect to the internet via S-1.

I want to have HAProxy to forward incomming traffic of the users via a random proxy amoung PR-s with 2 conditions:

1. only when there's certain, pre-defined keyword in the URL, traffic must be routed via a proxy.
2. In all other cases, it must go to a requested resource directly as is, without a proxy

How would I implement this?

(1) client -> HaProxy -> if keyword --> sub-proxy (random) -> website

(2) client -> HaProxy -> if no keyword --> website