[trevius]

This is a modified version of something I use for a fun encounter I setup recently. It should work for you:

sub EVENT_ENTER {

my $player = $entity_list->GetClientByID($userid);
my $get_player = $player->CastToClient();
my $player_hps = $get_player->GetHPRatio();

  if ($player_hps <= 70) 	{
    $npc->SetAppearance(1);
    quest::say("Healer available. I'm inside the gate, near the causeway to the wall.");
  }
}