OTOH IO::Socket::INET buys 14 years of backwards compatability

I'm aware of that. But frankly, any system too old to run at least Perl 5.20 with IO::Socket::IP and IPv6 (at least have support for it) is probably a major security disaster waiting to happen. For one thing, it probably still uses SSLv1 or no encryption at all.

I know there are always legitimate business reasons to run such old systems, but these days they they become overshadowed by the risk involved. Just thinking of Facebook here. Because they didn't patch a data leak when they first noticed the possibility, they might have to pay the EU a penalty of over a billion Euros. And thats just the government side, civil lawsuits may follow. That was a somewhat recent security issue, i somewhat doubt government would be more lenient if you run code that has issues for which patches are out for over a decade...