...or, I was re-writing a module to be v5.6.0 compliant while I created the examples for this module, and wasn't quite there yet, or, FreeBSD has some issues with locking files, which is what I may have been debugging in the module I based these examples on ;)

Well, I was thinking that one might get a Perl module from CPAN and it would install under some Perl versions and/or flavours, but not others.

Yes, use brewbuild for that regardless of platform (you have to download/extract the module first), or just perlbrew exec cpanm Module::Name if on *nix or berrybrew cpanm Module::Name if on Windows.

The Test::BrewBuild software is more geared to developers, to test their own modules. However, it isn't limited to just devs, if you actually fetch the source of a module (and if you want distributed testing, have access to the git repo that contains the module's source). Either way, perlbrew, berrybrew are spectacular resources to ensure a module will install properly on a system Perl, without affecting the system perl. The distributed nature of Test::BrewBuild was an early idea, pushed forward by a request.