alias thop {
  if (!$regex($nick($chan,$nick).pnick,[~\&@%\+])) return $chr(160)
  if ($regex($nick($chan,$nick).pnick,[~\&@%\+])) return $left($nick($chan,$nick).pnick,1) 
}

Can't you just use this?

alias thop return $iif($left($nick($chan,$nick).pnick,1) isin ~&@%+,$v1,$chr(160))

99.9% less regex with 0 calories!