I tried to bring the tcl.m4 file, etc up to date
in the iwidgets package. I grabbed the fossil tip
of tcl.m4, dropped it in place, and ran autoconf 2.59
to generate a configure script.

Then when running that configure script, I get these
errors:

configure: creating ./config.status
./config.status: line 303: SHELL: command not found
./config.status: line 303: srcdir: command not found

It appears to be complaining about this line in config.status:

INSTALL="$(SHELL) -c"

That's all I know.