- Never heard about such docs. Anyway in my experience perldeltas are not sufficient. I have quite good understanding of what is allowed in old Perls but still I've biten a couple of times by bugs in old Perls. I.e. being developing on 5.6.1 and using 5.005 supported syntax I found my code to don't work on 5.005 because of bugs in this version. The only way to ensure compatibility is having 100% coverage tests and run them on all supported versions of Perl.
- I think most Linux distros have 5.6.1, FreeBSD still at 5.005 (though it is possible to get 5.6.1 from port). Commercial Unices are very conservative. I've heard some of them still bundle Perl 4! So I think most their users install Perl themselves anyway.
- Really depends on your target audience. If it is your internal project to be used in, say, inside your company than it probably is not hard to require specific version. On the other hand company I'm working for right now has a Perl project our customer explictly requires 5.004 (!) compatiblity. Shortly speaking it is a plugin for customer's shopping cart targeted for wide audience. When I've beeing discussed Perl version requirements for this software they said they still have a lot of support calls from users with this version of Perl. Requiring even 5.005 means lost money.
--
Ilya Martynov
(http://martynov.org/)