GTM load balancing based on source IPv6

Something like this:

when DNS_REQUEST {
    log local0. "GTM LOGGING: DNS request matching test.com  [IP::remote_addr] - QUESTION:[DNS::question name], [DNS::question type]"
    set ipaddress [lindex [split [IP::client_addr] "%"] 0]
    set last [lindex [split $ipaddress ":"] 7]
    set lastdec [expr 0x$last]
    log local0. "8th hextet $last ($lastdec)"
    if { ( $lastdec%2 ) } { set destination "odd" } else { set destination "even" }
    if {$destination equals "even"} {
        pool pool1
    }
    else {
        pool pool2
    }
}