on *:CONNECT:{
set %con 1
while (%con <= $lines(ajoin.txt)) {
join $read(ajoin.txt,%con))
inc %con 1
}
}

You don\'t need to do that:
on *:CONNECT:.play -cs ajoin.txt

You could also expand this script by writing to a different filename for different networks (something like write ajoin. $+ $network $+ .txt $did(2) instead).

If you did that, you could make the connection part be something like this:
on *:CONNECT:.play -cs ajoin. $+ $network $+ .txt

Good idea, Akishoot. :)