I know what you mean. Once someone gets used to something, they can be pretty close to the problem and not explain it well. You might want to check out my CGI course (link is below), but since I don't know what level you're at, it still might be a bit advanced for you. Lesson two explains what you "did wrong". However, I wouldn't say you did anything wrong if you didn't know. After you read lesson 2, you should have a slight idea of what the issue is, but if you're too new to Perl, it might seem a bit daunting.

Good luck!