Ooh, I didn't know you could nest 'em! ChatGPT never told me that! Now we're getting somewhere! :)

    echo "${1:-${env_var:?I need a value for that!}}"

That is awesome! :)

Like massively concise construct. I don't know what other language can compete:

  console.log(process.argv[2] || process.env.VAR || console.error("I need a value for that"));

I personally prefer the bash v