It means that for basic stuff they are pretty much the same. Variables & data structures (scalars, arrays, mappings), creating and calling functions, creating and instantiating classes, looping, if/then/else, talking to the network, talking to the OS, talking to the db, etc. This basic stuff is in all these languages; the only real differences are in the syntax (and that's not even very different).
For many programming tasks, you're just doing these basics over and over again. Any language will work, so you may as well pick one that's got it where it counts -- modules, since that will make the most difference in how much extra code you have to write. And Perl wins that competition with the CPAN.
> Would they have gone off in search of the Holy Grail with Perl 6 ...
Thing is, it's not a Holy Grail. It's just the next revision of Perl. Take a look at some example Perl 6 code online; they've cleaned things up, fixed some boo-boos, and upon seeing it I expect you'll matter-of-factly say, "oh, yeah, still looks like Perl :)".
http://en.wikipedia.org/wiki/Perl6#Goals
Sure, at some high-level they're all the same, but the devil is in the details. Just saying they're all the same is specious.
If you have some specific questions, I suggest asking them at http://perl6.org/community/irc , which I've found to be very friendly and helpful.
I am genuinely curious where you got your ideas about on perl usage?
Regardless of growth or decline in any of Perl, Python, and Ruby, my opinion is they're so equivalent it's barely worth discussing them separately. Pick the one that has the libraries and frameworks you need. It so happens that http://search.cpan.org is the easiest way to check up on libraries for any of the languages.
Perl6, if they ever pull off a fast and stable release, is another matter. It's likely to be a game changer. I actually quite dislike this perl5i thing and the declarex syntax changing modules in general because they needlessly fragment the language.