dkfellows

Tcl has a bigger footprint than Lua, but provides more services.

The string interconvertibility (more formally, strings are the supertype of all other value types) only really applies to values that you can regard as being immutable. Mutable state instead goes into a named entity (even if it is an automatically-generated name); after all, if you can mutate the state, you need to care about the actual identity of the thing that holds that mutable entity. It also means that there's very little of the old spooky action-at-a-distance problems with Tcl; it's always clear where you are dealing with something that can confuse you, as you've explicitly got a name/handle.

Tcl did solve the problem of handling double-precision floating point number precision loss well. A numerical analyst fixed the code so that the automatic conversion generates the shortest string representation that will reparse to the same bit representation. It also avoids quite a few bugs in the C library in the process (on the grounds that different platforms have different bugs to each other).

If someone wants to use, say, LuaJIT to work on the $100k bounty for a 10x speedup of the Tcl language, they should go right ahead; prove that you can do it and claim the cash. (I guess I'll be rather involved in setting the test of the performance up; I've relevant experience.) However, that scale of acceleration is not trivial, not at all.