Making Lisp dialects is great for trying out those all those ideas you get for programming languages.
My current idea is a form of inherently concurrent language shaped around the idea that expressions can have more than one value.
This is NOT equivalent to a list, array or iterator. Those come separately.
Think instead of fuzzy logic or the qubit of a quantum computer. If you use if-then-else to branch on a qubit, you evaluate two branches at once and there are now parallel code paths.