Do Perl people develop tunnel vision? As always, It Depends.
Some people certainly will.
I find that Perl exposed me to new concepts and sparked my interest in looking beyond my horizon in the first place. It opened up the world of list oriented programming; I definitely want to learn LISP and maybe other functional languages now. Its nuts-and-bolts approach to OO opened my eyes to problems, choices and design decisions in OO design I didn't even notice in more traditional OO languages before. Together with the fact that Ruby's proclaimed aim is to be the better Perl, that made me go and learn that language, making me appreciate the "blackbox", BDSM approach to OO more from a different point of view. That's whence my resurfaced interest in learning Smalltalk at some point came from. For good measure, I want to see what declarative programming a la Prolog is all about.
All that said, I will probably keep coming back to Perl. I don't think that implies tunnel vision. Many ideas that work in one language work in another too - one just needs the expertise to translate. Closures are to LISP what anonymous classes are to Java. Much the same way, many ideas can be "backported" to Perl.
In my case, Perl was a powerful catalyst for developing my senses and skills. I believe it depends on the coder more than on the language whether they will develop tunnel vision. I don't think other languages make developing tunnel vision a lot harder than Perl. They just amplify the effects of tunnel vision, where Perl at least lets you get by somehow, someway, anyway. Whether that's good or bad is again debatable; with other languages, you may find yourself having to move to something else sooner. Much in this argument is a matter of priorities.
As for the exceptions vs the masses - I believe most of the prominent figures in Perl are quite open. Tilly and Dominous are strong advocates of functional programming. Larry has taken and keeps taking from other languages (latest example - some stuff from Ruby). Those are just the most obvious examples that come to mind.
As for the mindset among the less prominent masses in the community.. you probably have a point there. I don't think there's much that can be done about this though. I just sit back and thank Larry that the community frontmen are more openminded.
The fact that CPAN lowers the barriers for people to throw together solutions - I think that's ok. Some of them will develop an interest and grow to become good programmers. Others won't, but hey, they got their job done that way, and that's probably just as much as they're interested in. If it weren't for Perl, they'd just patch something together using other tools.
That's my view on things. :)
Makeshifts last the longest.