{ abc }: {

  a1 = let
    a = 123;
  in {
    b = 123;
  };

  a2 = let inherit (builtins) mapAttrs; in {
    b = 123;
  };

  a3 = abc: let
    xyz = 123;
  in {
    abc = 123;
  };

  a4 = let x = 5; in {
    y = x;
  };

  a5 = let x = 5; in x + 5;

  a5 = let
    x = 5;
  in if x == t then 10 else null;


  a6 = obj: {
    x = 5;
  } // obj;

}

In reply to @blaggacao:matrix.org
I have to pick which kettle to put on the stove. Out of principle, I'm agnostic to whatever formatting as long as it's canonical. Hence, I'd have to leave that discussion to others. 😆

In reply to @timdeh:matrix.org
I'd be interested to analyze it's formal worst case complexity in comparison to the module system 🤔