I know of people who are stuck with 5.6 (AIX?)

I can only confirm. I have been stuck for years with 5.8 on old AIX servers (until we moved to Linux RHEL servers about 18 months ago), and we're still stuck with Perl 5.8 on several VMS servers (please, don't laugh, these VMS servers host the main business application of one of the largest telecommunication operators in Europe).