DID NOT WORK:
var %tbn = @buffer. $+ $left($nopath(%map.draw.fill),-4)
window -Bhp +d @!! 0 0 0 0
renwin @!! %tbn
DID NOT WORK:
var %tbn = @buffer. $+ $left($nopath(%map.draw.fill),-4)
window -Bhp +d %tbn 0 0 0 0
WORKED:
%tbn = @buffer. $+ $left($nopath(%map.draw.fill),-4)
window -Bhp +d @!! 0 0 0 0
renwin @!! %tbn
WORKED:
%tbn = @buffer. $+ $left($nopath(%map.draw.fill),-4)
window -Bhp +d %tbn 0 0 0 0
NOTE:
The presence of /var is the ONLY thing that changed, for the offending routine to be successful. The given lines appeared exactly as I've shown you.

mIRC 6.17, win2k

I can't reproduce any of your local var-related problems. Make sure you don't have a /var alias somewhere (you can check this with $isalias(var).fname).