Returning value of spell ID

[Township EQ]

I'm trying to use the sub EVENT_CAST_ON for one of my NPCs, my issue is that I can't seem to figure out how to make the script recognize a spell.

My current trainwreck:

sub EVENT_CAST_ON {

         my $spell = $npc->GetSpellID();

        if($spell = 200) {
             quest:say("you did it blah blah");
        }
}

Now obviously GetSpellID is not even a thing, i'm wondering if there is something that I can put there.. This is just a test for minor healing to make him do stuff. If there is no other way I suppose I can make a script for this specific spell to signal the npc to make him do what I want. someone halp?