Sorry if it's been requested before...
This works...
alias setsig { set -u5 %~Signal SIGTEST1 | signal %~Signal }
on *:signal:%~Signal:{ echo -a Signal Name: $signal }
This doesn't, but I wish did...
alias sigtest { return SIGTEST2 }
alias dosig { signal $sigtest }
on *:signal:$sigtest:{ echo -a Signal Name: $signal }