Forking is expensive. Avoid it if you're on a loaded machine, or expect the computer to become loaded (always expect your site to grow large, at least in code design).
Mirroring a single file is easy:

use LWP::Simple;
mirror($url, $filename);
[download]

Undoubtedly, there are recursive solutions on CPAN.

- Yes, I reinvent wheels.
- Spam: Visit eurotraQ.