We try to create several triggers like:
{routing-health:get-gate.sh[{$HOPS},{$IP}].last()}<>{$GATE}
{routing-health:get-gate.sh[{$HOPS1},{$IP1}].last()}<>{routing-health:get-gate.sh[{$HOPS2},{$IP2}].prev()}

get-gate.sh - external script, return IP of HOP N.

So errors showed by zabbix:
Cannot evaluate expression: macro '{$GATE}' value is not numeric.
Cannot evaluate expression: expected numeric token at "127.0.0.1)<>(127.0.0.1)"
& etc.

According to https://www.zabbix.com/documentation/3.2/manual/appendix/triggers/functions
Zabbix must NOT expect numeric or other values, for fuction last()/prev() and AFAIK must respect item type in the check.

Nope, i don't test this with other zabbix versions.
Thanks.