Line numbers serve some purposes, both as labels and as reference points for errors. Fortunately, we don't need to hardcode the numbers in anymore to get either of these benefits. Perl has labels to put on blocks, should you want one for a goto or whatever. Any decent text editor (well, since I only use emacs, this is my yardstick for decent) should be able to tell you what line the cursor is on-- allowing you to find the point at which the error occurred.
As others have said, line numbering is quite annoying if you need to reorder or refactor your code, since changing them (and only them) is probably necessary. In fact, I'm now having flashbacks to programming my C-64. Thanks a lot! ;)