Ooofff! That's a whole slew of requirements. Extensive PERL experience is even needed, along with Ruby and Sinatra. I guess Full Stack Developer is not enough anymore nowadays: you have to be a Total Stack Developer 🤪

But that being said, any software engineer is faced with that phenomenon every day. For example, nowadays I'm very proficient in Python and PHP and C/C++, and I started learning Clojure/ClojureScript some time ago. In comes a new assignment which requires hardcore JavaScript (not jQuery!) and guess what, I'm able to pick that up in a week or so. I'm surprised of myself. Something I noticed before: learning new programming languages doesn't make you forget the ones you already know.