The following code will output Ruby is a great language!

a="Perl"
def a.+ other
  "Ruby"+other
end
a+=" is a  great language!\n"
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So, ruby does actually allow you to extend and redefine it's built-classes.. the example also works if you define a new class which inherits String, instead of using singleton style inheritance.. I have not however tested this with every built-in class, but those I have tried it with, worked fine!

Or am I just confusing it with that so-called OO language being hyped by Sun? {grin}
He he... probably... I have had alot of beginners getting really confused over the hybrid style of Java...