Programming Perl, 4th Edition

Error Indications

If you want your function to return in such a way that the caller will realize there’s been an error, the most natural way to do this in Perl is to use a bare return statement without an argument. That way when the function is used in scalar context, the caller gets undef; when used in list context, the caller gets a null list.

Under extraordinary circumstances, you might choose to raise an exception to indicate an error. Use this measure sparingly, though; otherwise, your whole program will be littered with exception handlers. For example, failing to open a file in a generic file-opening function is hardly an exceptional event. However, ignoring that failure might well be. The wantarray built-in returns undef if your function was called in void context, so you can tell if you’re being ignored:

if ($something_went_awry) {
     return if defined wantarray;  # good, not void context.
     die "Pay attention to my error, you danglesocket!!!\n";
 }