I found perldoc.pl with a high usability level being up-to-date to version 5.30.0.
Perl.org links to perldoc.perl.org which stops at version 5.26.1. But on the other hand, it links to Download (version 5.28.2) to Strawberry Perl (actually version 5.30.0) which I find very confusing.
I already know that Perl 6 is a completely different language. Is there maybe another language barrier after 5.26.*?
Since I use it rarely, a program update is the starting point when I reenter Perl. And that's why I was interested in studying the delta documentation before installing, and this delta was hard to find.
The site at perldoc.perl.org is the "official" one (you can tell as it's on the perl.org domain), but that site is run by someone outside of the Perl Foundation and it seems that they have been too busy to update the site recently. I believe that perldoc.pl is an alternative project that was set up when it was noticed that the older site was no longer being kept up to date.
Actually, you can always get the most up-to-date and official documents on CPAN.