I don't get too excited about any new feature in Perl until it's survived a couple of major versions. A lot of things only sound like good ideas but disappear in the next version. Pseudo-hashes, for instance, died (thankfully), although I still have to deal with their insidiousness with the right versions of Perl.
Some other things I don't use and haven't seen mentioned:
- our(): I can see the reason for our(), but most people don't use it to unmask a package variable. They use it so they don't have to use vars. That sacrifices backward compatibility for no good reason.
- overloaded operators: I like overloaded operators and I think they are a lot of fun to play with, but I just don't think people think about Perl like that. I probably think about this because I learned about that sort of thing when I did C++ where I could overload based on object types. Since Perl think differently, I don't think people are expecting that. For instance, if I want to print a reference (on purpose, to debug or whatever), I don't want magic stringification. I can see the usefulness of that, but most Perl things don't do that so I don't expect it.
- Exceptions: I think exceptions would be tolerable if everyone used them and they were built into the language, but not everyone does and they aren't. Perl is much more like C than C++. I'd rather have consistent expectations across modules than a list of modules where I have to remember to wrap everything in eval.
- Source filters: Actually, I don't use much of anything Damian writes, but it doesn't have to do with the code quality, really. Some people get excited about his cool hacks, but can't seperate his production-useful stuff from the cool proof-of-concept hacks. They end up using anything from TheDamian, and some of them shouldn't be used for anything that anyone else has to maintain (and that's just about everything). I pretend none of that stuff exists so I don't spread the word. It's cool stuff: I just don't want to ever maintain it.