instead of
use
%money_ $+ [ $+ [ $nick ] ]
or (when setting)
If you use the last method (which is my preferred method), to get the value, you have to double evaluate the variable, thus you would use
or
$eval($+(%,money_,$nick),2)
6.02 is such an old version, that it sounds like your script was taking advantage of a bug, which has been fixed in the mean time.