If your code base now runs on perl 5.8 only, eventually you will have to upgrade. At some point in the future you'll have new hardware on which the legacy OS that come with legacy perl won't boot anymore, so it's not a question whether you upgrade, but when.
With that in mind, advice of the form "Upgrade to at least perl 5.12 because it fixes your $problem" is actually quite valuable, because it gives you reason not delay the upgrade any longer.
Also the more incentive you have to upgrade, the easier it becomes to convince your manager that now would be a good time to spend your resources on upgrading to a newer version of perl. And a list of issues that would be much easier to fix with a newer version of perl is exactly the kind of incentive that convinces managers.