GNU `m4' is an implementation of the traditional UNIX macro processor. It is mostly SVR4 compatible, although it has some extensions (for example, handling more than 9 positional parameters to macros). `m4' also has builtin functions for including files, running shell commands, doing arithmetic, etc. Autoconf needs GNU `m4' for generating `configure' scripts, but not for running them. GNU `m4' was originally written by Rene Seindal, with subsequent changes by Franc,ois Pinard and other volunteers on the Internet. All names and email addresses can be found in the file `THANKS' from the GNU `m4' distribution. This is release 1.4. It is now to be considered stable, future releases are only meant to fix bugs, increase speed, or improve documentation. However... An experimental feature, which would improve `m4' usefulness, allows for changing the syntax for what is a "word" in `m4'. You should use: ./configure --enable-changeword if you want this feature compiled in. The current implementation slows down `m4' considerably and is hardly acceptable. So, it might go away, do not count on it yet.