Java has a lot of "industrial-strength" libraries. It would be very interesting to be able to use them from a language such as Perl6 natively. All of Java's stuff would be a vast addition to CPAN.
One of the reasons that really irritated me about programming in Perl 5 some 3-4 years ago was that it was clearly falling behind in terms of supporting some xml-based technologies, or pdf generation, or microsoft excel interoperability, and all such stuff which the primary competition in that space (java) had no trouble with, and which were features that the customers were requesting. I have no reason to think the situation has got any better, because my impression is that Perl's popularity has been falling further since.