In coordination with /run -a, it might be useful to have an identifier to indicate whether mIRC itself is running with elevated privileges. Perhaps $isadmin or $iselevated.
The status of mIRC itself has an effect on the /run -a command. If mIRC itself is running as admin already, /run's -a switch doesn't trigger the UAC prompt.
Also, if mIRC itself is running as administrator, then programs launched with the /run command seem to be given admin privileges automagically, regardless whether using the -a switch. I hadn't realized launched programs were also inheriting admin mode since the UAC prompt didn't pop up. I assume that's the default and it's not feasible to have a switch to not let the target program inherit the admin privileges possessed by mIRC itself running in admin mode.