Well, for one we can name the file configure.ac rather than configure.in. That'll cause immediate breakage if you use autoconf 2.13 or older and would also indicate immediately to the compiling party that autoconf 2.5x is needed (also I think many distributions have wrapper scripts that automatically use the right autoconf version if it sees .ac rather than .in).
/ David Hedbor
Previous text:
2003-01-09 14:12: Subject: autoheader
But you don't object to using the language "autoconf2.50" per se? It shouldn't be too much trouble to make run_autoconf check whether the binary "autoconf" implements the language "autoconf2.50" or not, and bail out if it doesn't. Other packages tend to do this.
/ Marcus Comstedt (ACROSS) (Hail Ilpalazzo!)