[This is a part of Tclx's package]
Does auto_load_file work in the current Tclx? All I get is a tcl message about it being an invalid command.
The tclx.tcl file clearly declines to source the autoload.tcl file.
There's also clearly no tclIndex file to establish autoloading by the conventional means.
Whether that's always been true, or when it might have changed, I can't say.
Tclx 8.3 worked, but since then, I think, it has been broken. I'll open a bug report - thanks!
I have a built-from-source version of Tclx 8.3 which worked back in the ancient of days. But the auto_load_file, and perhaps a few other things, appear to have stopped working, both in the "from source" builds and in ActiveTcl, some time back. I'm going to attempt to figure out what all doesn't work.