I'm a Perl Newbie. Please no tomatoes...

Ketchup?

When I try to run the script from the command line, I get an error saying the package doesn't exist. Is the package replaced for a 64 bit OS? Do I need to get the package from somewhere and somehow compile into Perl?

Yes, the module needs to be installed, they always do, its mostly cpan Win32::Process::Info and variations thereof ( ppm Win32-Process-Info )

Reading material

links here like How to install CPAN modules into ActivePerl

Yes, even you can use CPAN, A Guide to Installing Modules, Top 11 (GOOD) reasons not to use someone else's Modules, Top Seven (Bad) Reasons Not To Use Modules