i'm not sure , but try this :$ improve me if I'm wrong

on *:TEXT:!ajoin*:#: {
  if ($nick == <bot_owner_nick>) {  
    if ($2 == add) {
      if ($istok(%auto.channels,$3,44)) {
      }
      else {
        set %auto.channels $addtok(%auto.channels,$3,44)
        msg $chan 8,12I add $3 to my ajoin list !
        join $3
      }
    }
    elseif ($2 == del) {
      if ($istok(%auto.channels,$3,44)) {
        set %auto.channels $remtok(%auto.channels,$3,44)
        msg $chan 8,12I deleted $3 from my ajoin list !
        part $3
      }
    }
  }
}