This is a must-read for any Perl programmer. You are only as good as the teachers you have, and if your teachers use stuff like $|++, you are screwed. In this case, Conway would tell you to Use English;, and then you'd know what a $| is. A sampling of other tips:
Don't modify via $_ (too easy to screw things up)
Use hashes for arguments if arguments > 3 (trackability)
Use Croak instead of die (Croak gives more info, better for debugging)
Use ' ' instead of " " when no interpolation (less ambiguity)
Don't use unless (complication and confusion).
use /xms in regexes (for readability, and avoiding mistakes)
test when closing or opening a file
A few of the reviews here are 1 star. IMO these are people to which "freedom" is more important than "group code maintainability". This should really be the third Perl book for anybody, after Learning Perl and Intermediate Perl.
For those wanting to test their code against this book, there is a Perl Module, Perl::Critic, that does the job.