Not unless you declare a version. Old style perl will continue to work as before.
If you declare something like:
use v5.40;
Your 20 year old script can continue to run just fine.
Some--not all--of the people working on perl really want so-called "cruft" to disappear. I'm not a fan of that attitude for such an old language with such a rich history of backwards-compatibility, and I definitely don't think it's going to accomplish some kind of perl renaissance. I think it would be better to double down on what makes perl unique. When I watch Signes giving a talk like https://www.youtube.com/watch?v=FlGpiS39NMY where he shakes his head at variables like `$;` or `$,` (29:20 in the video) ... it looks like the leaders of perl hate how strange it is. That worries people like me, who love perl _because_ of its quirkiness, not in spite of it. Surely people who want something more consistent have moved to Ruby long ago.
Personally, so long as all that stuff's behind a feature bundle I'm all in favour of it.
A little nitpick: it's not about "multidimensional hashes", but rather "multidimensional array emulation". Steer clear of it, if you can.
I personally don't mind using variables like $; or whatever. Some prefer to "use English" and use longer variables name for the same effect. More power to them.
I just wrap the call with the proper "## no critic (...)" and off I go.
I have a feeling you're reading Richardo Signes wrong, by the way-- he likes to play up what a negative kind-of-guy he is, and makes critical remarks about the state-of-perl in public that some people take a little too seriously. Perl-haters gotta hate, and they really loved to link to his talk with the title about how perl is an "Ongoing Disaster" or some such.
Feature bundles don't bother me, but if I read between the lines (possibly too much), comments they make seem like they are still looking for an opening to remove some of these features entirely. I hope I'm wrong.
(I remember the Ongoing Disaster talk, I personally thought it was fun)