Someone

on *:join:#:{
  set %chan $chan
  timer 1 1 /checkalice
}
alias checkalice {
  set %p 0
  while ($nick(%chan,%p)) {
    inc %p
    if ($regex($nick(%chan,%p),Alice-Bot) != 0) {
      part %chan I wont stay in a channel that already has a Alice-Bot.
      halt
    }
  }
}