Topas v6 includes string equations. Some examples:

                out_file  aac.out  ‘ This will throw an exception
                out_file = aac.out; ‘  This will throw an exception
                out_file = "aac.out";
                out_file = String(aac.out);
                out_file = If(Get(r_wp) < 10, "aac.out", "");
                out_file = If(Get(r_wp) < 10, Concat(String(INP_File), ".OUT"), ""); 

Some new string handling features are:

                prm aabb = 1.234;
                prm sasb = 4.321;
                prm sa = "aa";
                prm sb = "bb";
                prm sc = sb;
                prm = Variable_Name_From_String(Concat(sa, sc)); :  1.23400`
                prm = Variable_Name_From_String(Concat(String(sa), String(sb))); :  4.32100` 

String and Variable_Name_From_String are new functions.