sub EVENT_HP {
my $target = $npc->GetHateRandom(); #gets random hate from the hatelist
if ($hpevent <= 50 && $hpevent >= 49) { #check to make sure that a nuke or something wont skip the event
quest::setnexthpevent(25); #this sets the $hpevent values.  you would have to declare this earlier in your script, say when mob is aggroed for the 50% one to kick in, and yeah its by percentages.
     if ($target) {
          $npc->SpellFinished(6556, $target); #same spell as above for my sake :P
          }
     }
if ($hpevent <= 25 && $hpevent >= 24) { #we declared this when mob hit 50%
     if ($target) { #since we are using same target, should work just fine, could redeclare the variable as a different target (random, top etc) but then we would include them within each $hpevent, as opposed to the top of the sub.
          $npc->SpellFinished(6556, $target);
          }
     }
}