For those who think their code is bug-proof, I suggest stepping through your code and taking a second glance.

Almost ALWAYS, when you think your code is efficient and bug-free, don't be surprised to find a few inefficiencies, bugs, and a lot of uneeded code snippets.

In the past, I have seen people rewrite their code, deleteing tons of lines, replacing 10 lines with 1 or 2 and a lot more.
This is usually when someone tries to fix a script they wrote when they began perl (Same thing with any other language).

Here's what I say: Beginners it's okay to overdue it; you don't know better!
Advanced: look over your code and make it better!