modularizing a large Perl script

The Perl script I'm hacking at now at work promises to become very large. A few KLOCs at the least. I've written scripts up to about 1.5 KLOC before, all in one file, and my experience with it is that it's not simple to manage them. In such large files, it's not simple to conveniently find stuff. And, it's hard to have this picture of the whole thing in your head, which is important IMHO.

So, I'm planning to do it smarter, from the beginning, this time. I want to divide my script to modules. I'm just not sure how... it's 2 ways, as I see it, OO or just modules of related functions. Any ideas are welcome.