@if @eq($CHAIN, FORWARD) not working about ferm

[MaxKellermann]

Describe the symptom. Do you see a ferm error or does ferm silently omit the rule?
Also your sample omits necessary context. In which context do you write this rule?

@def $LOCAL_UDP = (domain);
domain (ip ip6) chain (INPUT FORWARD) {
policy DROP;
proto udp mod multiport destination-ports $LOCAL_UDP ACCEPT;
@if @eq($CHAIN, FORWARD) proto udp dport 123 ACCEPT;
}

Ferm return no error. The rule is silently omit.
There are are some more rules but this above should illustrate it.

[MaxKellermann]

This works with ferm 2.5.2, but you're using a ferm version that's 4 years old.