gnustandards just pulls in the canonical one in texinfo. In addition to what Paul said, I can report that I originally wrote the contrib/perldoc-all stuff (many years ago) as an exercise of pod2texi, and to have the perl documentation in texinfo. It was not canonical in any way.
I also don't know if it still works. I see in perldoc-all/README that "many internal links are missing" from the result. As far as I'm concerned the whole contrib/perldoc-all directory could (should?) be deleted. I doubt anyone is using it. -k
