Create an Irule action based on username

I have same idea

when HTTP_REQUEST { 
    Internal users 
    if { [IP::addr [IP::client_addr] equals "10.91.0.0/16"] } { 
        Access allowed 
    } else { 
        switch [string tolower [URI::query "?[HTTP::query]" "username"]] { 
            "admin" { 
                HTTP::respond 200 Content {
                    Acccess denied for admin account on external access
                } 
                return
            } 
            "apple" { 
                if { not ([IP::addr [IP::client_addr] equals "172.65.0.0/16"]) } { 
                    HTTP::respond 200 Content {
                        You are not on the proper subnet. Access denied.
                    } 
                    return 
                }
            }
        }
    }
}