Code should fail as early as possible to avoid collateral damage, and to help identify the source of a problem.
Using special return values will clutter the code with assertions, which decreases readability and increases the chance that you will miss an exceptional condition.
in reply to Use of "die" in OO modules
It is also difficult to come up with a consistent failure convention. Using undef is a bad idea as it is true in list context (any value is), and some functions will return undef as a valid response. -1 is less appropriate. You could bless an error object and return that, but that strikes me as an ugly solution.
I prefer to use Exception::Class, or if I am feeling lazy then die will do. Perl Best Practices has an excellent chapter on Error Handling (13) - I highly recommend it.