Well you see, the author already knows common lisp, is familiar with their own ad hoc DSL by virtue of having just come up with it, and refuses to learn jq.
Personally, I probably would've written '[.root[][1]]' for that problem myself though—not a huge fan of map/1.
1) I dislike that .[1] can be both an expression evaluated as a query and a "lambda". Really messes with my mind.
2) In my eyes, it's more intuitive because it looks like globbing and everybody knows globbing (this is the reason I use `**` too).
But yeah, this is a bit subjective. What isn't, though, is that I don't plan on adding much more than that; maybe merge, transform and an accessor using the same syntax. So if you know the host language, there's much less friction.