A look at perlhist
reveals that you probably witnessed Perl 5.6.1.
The hard way to learn the changes it to go through perld570delta, perl571delta, ... and read what changed. The much better approach is to pick a project and implement it in Perl.
Regarding Perl 6: The spec is quite solid at the moment, but the implementations are not finished. Pugs is the most advanced implementation, bad sadly abandoned. rakudo in the parrot repository is the rising star, but at the moment neither robust nor feature complete (but constantly improving).
It's certainly a nice language, but I'd still recommend Perl 5 for getting back to programming with Perl.