I've seen a fair few e-commerce (shopping cart based) implementations under Perl and I've yet to come across a really bad one.
At my last company we used Intershop (now called ePages I think) to build everything from small bookshops to large business-to-business stores for industrial parts. It's a bit of an expensive solution as it's a commerical application but it shows what's possible.
As to Perl being slow; that's a common misconception. Yes, Perl is slower than a natively compiled C/C++ program but it's fast enough for most applications and it's always been fairly effiecient at managing resources in my experience.
--- Jay
All code is untested unless otherwise stated.