{"ast_node_type":"variable","tokens":[{"end":49,"kind":"keyword","start":0,"text":"let"}]}
    let s = "The $0'th word $$ is: `$WORD` $!\n";
    use super::iter_subs;
    let subs: Vec<_> = iter_subs(s, 0).map(|sub| sub.translate().ok()).collect();