CHANGE THE HOST NAME IF THE CONNECT IS A POOL MEMBER

So if I understand you correctly, you're evaluating the URI to send to a pool, and you do this in the HTTP_REQUEST event. The LB events are triggered next and a pool member is selected. By the time you get to the HTTP_REQUEST_RELEASE event, you've already chosen a pool, selected a pool member, and can now alter the Host header going to that server based on the provided information.

when HTTP_REQUEST {
    if { [HTTP::uri] starts_with "/home" } {
        pool home_pool
    } else {
        pool other-pool
    }
}
when HTTP_REQUEST_RELEASE {
    switch [LB::server addr] {
        "10.70.0.1" {
            HTTP::header replace Host "server1:14002"
        }
        "10.70.0.2" {
            HTTP::header replace Host "server2:14002"
        }
    }   
}

If you also need to change the URI path, that can be done in either HTTP event with the HTTP::uri command. The ":14002" in the above is part of the Host header. Actual ports are defined in the individual pools and the VIP's port translation setting.