Even though it does not meet all of your requirements (yet), I would hate to see this discussion pass without mentioning GnuCash. It's by and large a personal accounting package at this point, with aims for small business functionality (including inventory management, payroll, etc).

The majority of the code is not Perl, though it does utilize several modules written in Perl.

Once the small business features are implemented, it remains to be seen how scalable it will be. Check out their list of goals for more information.

Matt