[catlifeonmars]

Two tricks. OP switched from programming to meta programming halfway through.

Also the reason given (not the right tool for the problem) was demonstrably false if we take the OP at face value. They solved it and their solution was robust to changing requirements.

We only know the OPs side of the story, but if we take it at face value it reads a lot like the interviewer wanted to jump them through hoops and they made the best of it. I would have politely declined the interview pretty early on if I was in their shoes.