I think you're a bit too focused on the "Real World Problem" part. If I can automate something with Perl on my home machine, I'll do that. An application to gather some statistics on my mail or something else: a nice little project. Are those important in the grand scheme of the universe? Of course not, but it helps me in a number of ways: saving time by letting the computer do what it does best, generating potentially useful information and honing my Perl skills.

On the subject of Summarizing an array of IP's you write:

"You could probably write a script/module which would handle the general case of this problem which would create a cute little organized data structure for input like this."

You know what? You probably could. And you would learn an awful lot about IP addressing in the process. Most of the time, you learn more about the problem domain of the problem you're solving than about programming. Remember, a programming language is a tool to get something done. Most of the time, it is not an end in itself (altough Perl can easily be ;-).

And while such an excercise might be wholesome, it would still be just that, an excercise. Never would anyone have a need for this type of functionality, and it certainly wouldn't make the world a better place. And if it was something that was interesting or useful, someone would have undoubtedly put it on CPAN already.

I work for an ISP and I think that this type of functionality could very well be useful. Most of the time, you aren't programming to make the world a better place, but just to get the job done.

Don't let the fact that someone already has done something similar be an obstacle for you to learning something new. As a novice, you're bound to do things that other people have already done. That's part of the learning process. And the fact that something similar is on CPAN doesn't necessarily mean that it's very good. Maybe you can come up with a much better way.

Arjen