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What other good beginner advice is bad intermediate advice?
I don't think that a good beginner advice has to be bad intermediate advice.
One of my advices when it comes to Perl is to join the comunity. It's one of the greatest I've ever seen.
From time to time I find a Perl programmer who doesn't know about the comunity nor about other Perl monks or even Perl books. Not rarely, that person considers him/herself a hot-shot!
It's in learning more and more that you realize how much more there is still to learn.
It's by staying confined in your small room, doing the same thing over and over again, that you convince yourself that there's nothing else to learn. And this is just wrong.
So my two advices at the moment are: Join the comunity and see what it has to offer and Try doing new things and explore new areas, don't be confined to the same thing over and over again (or otherwise, you'll get to the point where you say "I have three years or Perl", but you really have three months... repeated endlessly).