perform (mirc's) only works according to Network name and not server.

to findout your network name, type //echo -a $network
this should show network name (if it has one)

if you connect to server only (that does not belong to network)
perform wont work then, you should do your own scripting then
with ON CONNECT event:

on 1:CONNECT:{
if ($server == { do your login commands }