Simplify irule (rather than if ,elseif, elseif ...)

For scale-ability in the future if you ever needed to send traffic to other pools I would recommend creating your string data group with the URIs you want to match with values for the corresponding pool and use an iRule like this. I would also recommend setting the default pool on the virtual server itself.

when HTTP_REQUEST {
    if {[string tolower [HTTP::uri]] starts_with "/atm/"}{
        pool atm_HTTP
    }
    elseif {[class match [string tolower [HTTP::uri]] contains "/Common/my_uri_datagroup"]}{
        pool [class match -value [string tolower [HTTP::uri]] contains "/Common/my_uri_datagroup"]
    }
}