I think it's less what Perl 6 has that other languages don't have (almost everything is implemented in at least one language), and more that it implements everything together in one language. The pure breadth of what is supported is somewhat staggering. I posted the other day[1] about what I thought were some interesting features, so that might be a good start for some things that might set it apart.
1: https://news.ycombinator.com/item?id=10642153