Basic, only need one on text like:

on *:TEXT:*:#: {
  if ($1 == !join) { join $2 }
  elseif ($1 == !part) { part $2 }
}

Then again you could add some error checks like:

on *:TEXT:*:#: {
  if ($1 == !join) {
    if (!$2) { msg $chan No channel entered }
    if ($chr(35) !isin $2) { join $chr(35) $+ $2 }
    else { join $2 }
  }
}

And so on for !part