I maintain a few modules. Most of them are simple but one relies on quite a complex stack of other modules, being essentially a wrapper module.
My home systems are running Perl 5.10.0 as that's what comes with Debian Lenny. Yesterday I thought it best to try and create environments with Perl 5.8.8 and 5.6.2 on them so I could test the code on older Perls. I can not get the same level of coverage that CPANTester provide but I can weed out the worst bugs in advance.
Using VirtualBox I installed some older system inside a VM container and tried stuff out. Perl 5.6.1 era systems are a nightmare, not only is Perl old, but all the supporting libraries are old and the Perl modules my module is dependent on will not install because the overall antiquity of the system.
If you had an older system (RedHat 7 era) box that has been patched over the years it's possible to get partially there as some elements of the dependency stack are present, though at older levels. On a new system it's almost impossible to install anything as the more recent versions demand newer libraries that just aren't there...
Is it worth trying to support Perl 5.6.x...?