Note from THE FUTURE: Judd (author of PDL::IO::GD) fixed this in https://github.com/PDLPorters/pdl/commit/180854fd871f9b687fe277fea96897b6a202832e, which appeared in 2.4.10, and a Wayback Machine URL for the mailing-list discussion is at https://web.archive.org/web/20141030090655/http://mailman.jach.hawaii.edu/pipermail/perldl/2012-August/007113.html.

Shows how important (and valuable) it is to report bugs. Thanks, everyone!