It says in the document: "For more information on g-cpan.pl, please consult its man page." but there is no manpage for g-cpan.pl or g-cpan. There isn't even something about g-cpan in the portage man page :-( If you think this is a g-cpan bug, move the bug to the right section... Reproducible: Always Steps to Reproduce:
make sure your portage is up-to-date