Your question is slightly confusing, however these examples should help you out. I'll include both methods that use $eval and [ ].
%Myvar. [ $+ [ %var1 ] $+ . $+ [ %var2 ] ]
$eval($+(%,Myvar.,%var1,.,%var2),2)
%Myvar.var1.var2
% [ $+ [ %var1 ] $+ [ %var2 ] ]
$eval($+(%,%var1,%var2),2)
%var1var2
Good Luck.
- Raccoon