As both a Perl Monger and a WebObjects/Cocoa Developer I can say that they are different environments, each with their own strengths. I wish that Apple would get a RegularExpression module built strait into the NS environment like it is in Perl, but I wish that Perl's object orientation was even half of that either in Java or Obj-C.
If you are building regular apps, then Cocoa (I generally use Java) rocks, and Perl is no-where in sight (especially in the GUI and threading departments). If you are building CGI's without the WebObjects frameworks (or without a datatbase) then Perl wins. Perl also wins when it comes to writing run-once report generators.
Short Answer: Both Perl and Cocoa have their areas, and it depends on what you are doing. I can see the idea of having a Perl bridge being nice, but there are so many places where I can see it being a nasty mess (trying to figure out where to map scalar verses list context, etc...).