The language itself is very different, but Lua is a replacement for Tcl in the sense that it's a fairly simple and small language that can easily be embedded. i.e. it's about use cases rather than the language design.
I understand what you mean, but this is not the point I was trying to get across with my original comment. Maybe that's the reason why I haven't touched this subject. Although both languages can be easily embedded, the programming experience is still different, and there are still lots of "freestanding" systems in both languages, so the language design comparison still applies.
