While not Perl, about 10 years ago worked on a database/trading-analysis system written entirely in APL. It was a commercial system, running on Intel PC's of the day (286/386/486). Allowed for rapid development / changes, and customizations for each site. Had roughly 200 clients when I left. Not shrink-wrapped software, but good for their niche. A benefit of an interpreted language and remote-access software, was we could dial-up, step through the program, debug & fix. The curse of that environment was, we could dial-up, step through the program, debug & fix... the main developers often used customers as alpha-testers.