TCL is kinda similar to Rebol in some ways but in other ways it's the opposite of Rebol, because in TCL everything is a string (although it can ALSO have another type, thanks to clever shenanigans). (You probably knew this!)
The way things are done now (and have been for a long time), is that values are stored in a
struct Tcl_Obj{
int refCount; // objs can be shared
int myType; // indicates whether currently a long, double, etc
long longVal;
double dblVal;
[...]
char *stringRep;
int len;
}
So "native" (eg: longVal) values are used when appropriate, no marshalling back/forth between strings, but the string rep is always available (can be generated), because that's what Tcl promises: everything is representable as a string. This is what brings the homoiconicity to Tcl - logically it's just passing text tokens around, and emitting text tokens. Internally, again, more sophisticated, but you get the point.