if (%a = %b) {
;%a now holds %b
}
Eck, I'd hate to see side-effect assignment in mIRC scripting. It's shady enough in other programming languages, in a supposedly "newb-friendly" language like mIRC's it'd only cause trouble and abuse. It's also redundant since in 99% of cases you can use $v1 instead.
I personally always quite like it in other languages, $v1 loses some of its 'power' with nesting. Nothing that cant be worked around with an extra line of variable assigning just a matter of personal preference and i prefer side-effect assignment

I take back what i suggested earlier:
var %a = %b || %c
can easily be achieved with $iif and although i prefer the first in other languages upon reading back i don't think this would be beneficial for mIRC as long as strings are not strictly denoted.
One of those non well thought through brain storm shout outs :p
back on topic:
//if ($1 == (!game || $3)) echo -a what?
is already ambiguous in mIRC it doesn't
have to behave as
if ($1 == [ !game || $3 ] )
sort of speaking.