Apparently the perform options will do that now. However, I scripted this long beforehand.
on *:CONNECT:{
if ($network == Semi0NET) {
join #chans
commands
etc
}
if ($network == EFnet) {
join #chans
}
if ($network == Networknamehere) {
join #chans
}
}
If you dont know what the fuck that is, TOUGH, mIRC Scripting is a pile of its own piss.
Just replace the network names with your own nets that you use (to determine the net names type '//echo $network' when on a net) and add/delete if brackets as you please. NOTE: This WONT work on gamesnet as they dont provide a network name (nor do I think the on Connect will work as they dont provide an MOTD End statement).
Another script I use quite a lot is one to just get me back onto semi0NET whenever I start mIRC, and get me onto ZiRC (although I stopped going):
on *:START:{
/server irc.semicolon-zero.com
/server -m irc.zirc.org
}
also consider making a command using the above if statement structure to identify urself to NickServs on many nets.