It is a great language for quick and dirty scripts, one liners... But no one wants to start a big project in Perl, and I think for good reasons. With only the "quick and dirty" use case remaining, people didn't want to invest into a language for that, it is throwaway, that's the point. So it was left to die slowly.
I don't think that Perl 6 took away the Perl community, I don't think the people on Perl 5 and the ones on Perl 6 were of same kind, the former just wanted to continue using their "Swiss Army Chainsaw", while the latter wanted to design an innovative language. It has created some confusion, but I believe it is minor.
If I want to point at one thing that killed Perl, I would go with PHP. Websites were a common use case for bigger Perl projects. Now that PHP does it better, what's the point of Perl for that application?