> The chained script interpreter to be invoked
Chained is mentioned here but then also forgotten about: https://nixos.org/manual/nix/unstable/command-ref/nix-shell.html
Mostly it's unclear here why there are multiple weird hashbang lines there that are the same.
Also it's not great that here an entirely new construct is introduced that probably nobody will have ever seen before and to understand what it does you have to go to several different off-site documentation pages.
Can this be rewritten to be more standalone?