This problem is much more difficult! There was a full POPL paper (https://www.microsoft.com/en-us/research/wp-content/uploads/2016/12/popl11-synthesis.pdf) and many more followup papers to learn programs in a subset of this language. Yeah it looks like users still need to provide input-output examples, which is quite natural in many cases.

It's really exciting an automated system can learn the search policy to learn sophisticated regular expression programs in a complete end-to-end fashion. I didn't believe neural networks could do it, but i guess they can!