> The backwards incompatibility of Perl 6 absolutely killed Perl.

The insane lead time of Perl 6 to even get to a point of backwards incompatibility was it for me.

I'd started on an early version of perl 4 and went through the 5 transition and was excited about 6. For what seemed like "Duke Nukem Forever" time, and finally my fickleness drew me to other languages and frameworks.

I think more specifically it was the hesitance to move Perl 5 significantly forward in the meantime that caused the damage. That has been decidedly changed the last few years, with great strides being made. That time in between is lost, though.