%var = value doesn't work in command line because any command that starts with a variable/identifier in the command line is blocked for security reasons ($decode stuff). Unfortunately, at the moment, mirc can't distinguish between a variable being a command name or part of a variable assignment.
That's too bad. I hope Khaled will make an option to unlock these restrictions (being disabled by default as $decode, of course) or in some other way letting you set the security level.
