Ugh. What happened to the bracket formatting?
Also, there is no effective way for closing the client. For instance, if you needed to restart your computer, you would have to ensure that everyone was logged out of the bot first, or else manually change the values in udata.ini. Otherwise, when you opened the client running the script again, anyone who was logged on at the time you closed it would still be considered logged on, even if they had changed nicks or quit or whatever.
Hash tables are probably the easiest way to solve this problem since the data in a hash table is automatically cleared on exit unless explicitly saved. Therefore, even if the client crashes and the on EXIT event is not triggered, nobody will be logged in the next time you start the client.