I think Tcl strings aren't exactly what Perlis was talking about. First, the language knows how they're used, so there's a JIT (or whatever) behind the scenes eliminating the literal deserialize-process-serialize pattern you see in shell scripts. Second, a lot of Tcl data types (hash tables, sockets, etc) can be represented by strings but the string is just a simple reference to a rich internal structure. It's almost more like a pointer than a string in other languages.