Wims, I think it's you who's not getting it.
The idea is to create a dynamic variable name, even if it's only within the local scope. It works fine using '/set', but not with '/var'.
RoCK, does the non-$+() form work?
var -s % $+ var3. $+ %var2 = %var1
_OR_
var -s % [ $+ var3. $+ %var2 ] = %var1