Yes, this crossed my mind but didn't make it into my text.

So long as the standard tools for creating modules are inserting "use 5.008" or such into every new module they help create, there is little point in CPANTS testers using older versions of Perl. I wouldn't be surprised if some CPANTS testers have abandoned using old versions because so many modules fail.

But I think a movement to remove these useless and annoying cases of "use 5.008" (as opposed to the few cases that are there for real and documented reasons) could motivate a CPANTS revival for older versions of Perl. It has certainly sparked my interest in setting up CPANTS for 5.6.0 and 5.6.1. I'm sure there will also be challenges in getting CPANTS running in such environments.

I'm also collecting the few, simple, fairly easy techniques that I use (or avoid) in order to keep my modules compatible with older versions of Perl. Perhaps even a perlage.pod...