Yams is a Free shopping cart written in Perl, for use with MySql. I've never used it, but I recommend it highly on the strength of its cute logo.

O'Reilly's JavaScript Application Cookbook contains a sample shopping cart application. You may download it thus. Please don't ask me how I know this.

Using my secret device, I was able to find PerlShop, which turns out to be a Shopping Cart written in Perl. It's hosted by ARPAnet.com. Apparently the folks who founded the internet have found a more lucrative alternative to bake sales.

I have no experience with any of these. Good luck.