I know you meant it as a joke, but people often do know about the major features added in versions they don't yet have. Why? Well in the 5.005_03 to 5.6 transition, it was because people picked up the third Camel which was 5.6 specific. Another source is that you pick up code somewhere and it was written by someone with a further along version than you have. You try to figure out what is wrong, and if you pick up the wrong documentation, you can get very confused. Similar to that, new shiny features generate lots of discussion. People passing by see the discussion and don't always understand that those are shiny features that they don't have. Another variation is that programmers can hear about lots of shiny features in places like this, but the place they work is deliberately using an older version. (eg Because they don't want to go through QAing a transition yet.)
So yes, it is very common for programmers to know about major features that they don't currently have. And it is very important for them to be able to lay hands on documentation for what they DO have.
And to make an obvious note, what I am describing applies to any kind of software platform, not just Perl. With proprietary software you can add the fact that the company is usually distributing marketing material which is either for something you haven't upgraded to, or is for stuff that you only get on the more expensive plan. Given that nobody is charging you an arm and a leg for Perl, it is easier to put your hands on the latest and greatest. So the problem is less here, but not much so...
