perlhist contains a list of all Perl 5 releases, including dates. Differences between versions are documented in perl588delta, perl587delta etc.

Note that from the point of view of the perl 5 porters, only the source releases are official, while all other things (like ActiveState perl, the perl that ships with Debian etc.) are packaged up by third parties, and are not offical (though some of them are officially broken :-)