[mwmdragon]

Try using quotes around the variable like this

sub EVENT_SPAWN
{
  quest::SetNextHPEvent("50");
}

sub EVENT_HP
{
  if ($eventhp<=50)
  {
    quest::say("EVENT_HP fired");
  }
}

I found that most commands worked if you encapsulated teh variables in quotations. Hope it works for ya.