The point is that occasionally new features of Perl can only be released by restricting old syntax which might result in ambiguous parsing.
But P5P isn't that careless: All modules undergo regression tests with every version of Perl. The results for CAD::Drawing can be seen here:
As you see, it is well known that this module fails with all Perls starting from 5.18.2. And since then, as far as I know, the registered maintainer of the CPAN module should have received an email report about the failure.
Like Corion wrote, the fix is dead simple. So, if you know how to contact the author, it doesn't hurt to nudge him (again). He did the latest release in 2006, but might still be willing to maintain the module.