Mine

on *:join:#:{
  if ($nick == $me) {
    set %chanjoined $chan
    timer 1 1 /checkusers
  }
}
Alias checkusers {
  if ($nick(%chanjoined,0) > 5) msg %chanjoined %chanjoined meets the 5+ users requirement! Users on %chanjoined $+ : $nick(%chanjoined,0)
  else {
    part %chanjoined
  }
}