I can imagine a simple perl (or python or whatever) script that would run
through groff input, determine which preprocessors are *actually* needed,
and set up a pipeline to run through (only) the needed preprocessors in the
proper order. I wouldn't have to tell groff what preprocessors I think are
needed, and groff wouldn't have to change (although my script would) when
another preprocessor comes into existence. Modern processors are fast
enough, and groff input small enough, that the "extra" pass wouldn't be
burdensome. And it would take the burden off me to remember exactly which
preprocessors are essential. -- jpl