To use this Perl script you need an installation of Perl and the modules LWP and Mechanize. All of these should be free, if you're asked to pay for them you're doing something wrong.
I recommend ActivePerl for Windows. I've never used Perl on a Mac or Linux so I can't help you there. If you have success running this script on either, please let me know so I can update this with how you did it.
So you will need:
- an easy to install version of Perl
- a Perl module used for fetching web pages
- a Perl module that uses LWP and expands on it
Instructions for installing Perl modules are available here
on cpan.org. Some users have had real problems with installing these and getting mechanize working, dependencies etc. All I can say is cross your fingers and toes, I had no problems so hopefully you wont either.