Ruby's "DSL" ability is what allowed Rails, in Perl 6 everything is a DSL. Even strings are written a customizable DSL. You can turn on and off string features, and add new ones. It goes even deeper than that, you can swap the parser out with a new one mid-parse. One implementing Ruby for example. ( While it is possible to do this today, this isn't specced yet, as the exact way to do this is still in flux to get it to the same quality as the rest of the language ) So in a sense, all programming languages can be thought of as a subset of Perl 6. ( There would be little point in doing this for assembly though, as it will probably have to be emulated in most cases ) This feature is usually only used to slightly alter the existing parser currently.
That isn't even the best part, many features from other high level languages have already been brought together in Perl 6, in a way that makes them seem as if they have always belonged together.
If you asked a random sampling of people about which feature that they like in Perl 6, you will probably get a different one from each.
All good questions. My personal answers boil down to "no need" (to switch), "see the rest of this thread" (to read what promise Perl 6 might have), and perhaps https://docs.perl6.org/language/rb-nutshell (to read how someone familiar with Ruby explains how to map Ruby knowledge on to Perl 6).
So why do it? Mainly, if the framework I'm currently using can't do things I need to do, or if it's incredibly painful to use. To the extent that someone has neither of those problems, a new language is a cure worse than the disease, whatever its benefits.
Look at it this way... imagine there's a rib joint across the street. It may not have the best bbq, but it's there. Do I walk across the street for bbq, or do I drive halfway across town to get slightly better? I'll take what's there, thank you. Now, if I'm a vegan, I'll get up and go somewhere else.
JavaScript, for all its blecherous losing horror, had a compelling use case - it ran in browsers. Later, Node became a compelling use case, for dealing with both performance issues and package management problems that plagued other systems (including Rails).
Python had multiple compelling use cases. It became very popular in math programming and teaching, for its clarity and consistency.
Perl's compelling use case was with Perl 4, as a general purpose glue scripting language in a Unix world. It solved tremendous problems. Perl 5 didn't have a compelling case, and it grossly exaggerated the already bad problems with complexity and inconsistency. Am I talking about Perl 5? Yes, because for 22 YEARS, we've been saddled with that crap. Two decades of waiting for Perl 6, for Perl to unfuck itself and become something useful for more than one person at a time. That's like, my entire career. Longer than most programmers in this industry have been in the industry. Longer than some of them have been alive. 22 years.
So why, why, why should I switch? What's the promise now? What problem am I having with Ruby that it can solve?