I wrote my first online store with shopping cart in the mid-90's using just the CGI spec from the old NCSA server, a dog-eared copy of the Camel book, and a pile of perl scripts. At the time the only "online stores" were Egghead.com and Internet.net. I spent a lot of time reading the URL parameters of these two sites before I worked out how to create a shopping cart of my own.
I wrote it just on a whim for the computer sales company I was working for at the time. I had the store fully working and taking orders -- it just needed to be kept up to date. The feedback I got back from the owners at the time was, "Why are you making this? It's just a fad. Nobody will ever put their credit card number into the Internet." So the online store died on the vine.
I believed in the potential of the Internet though, so I found a way to create a business for myself and kept at it. 30+ years later I'm still building web sites; now using the Ruby language -- in many ways an evolution of the original perl language I started out with.
This is the source code for that original online store. I just barely understood perl at the time, and now that I look at it, it's peppered with security holes. But I'm pretty sure that's how most people were doing it at a time when it was just us early pioneers trying to figure it all out.
[The last modified date on the file was May 29, 1996. If I recall correctly, I started writing it in late 1994/early 1995, putting in most of the work before I got married in mid-1995.]