Isn't TCL almost as fast as C for certain things, like strings, but slow in other ways, like recursion? I haven't tried to do any performance optimizations yet really.
Time to consider that your experience may be outdated. Wub, to take one example, is a pure-Tcl web server whose performance is comparable to Apache. Network latency in handling socket I/O swamps any differences in code execution speed.
I doubt very much it could compete with our Apache/IIS plugin module, which had quite a few architecture layers moved from Tcl into C throughout its life.
It can be fairly fast for many use cases (specially because of async processing) and it was the basis one of the original scalable web servers that implemented multi-threading https://en.wikipedia.org/wiki/AOLserver
We did not went out of business, I have not written that anywhere.
In fact, the .NET re-rewrite was quite successful and many of the people involved on that team went on to create a very successful product based on the field lessons we had with the Tcl version.
