Hey! You can already get that behavior by starting your regex with (?m). A multi_line method would be convenient to match regex's API though. I've added a "help wanted" label to this issue if anyone wants to contribute that work.

Interesting, ?m seems not work, it will stop before the first line break even if I only use r".*"

let text = "hello\nworld";
let re = Regex::new(r"(?m)(.*)").unwrap();
let caps = re.captures(text).unwrap().unwrap();
dbg!(&caps);
dbg!(&caps.get(0).unwrap().as_str());

Ah, sounds like you want dot_matches_new_line which is (?s):

$ cargo run --example toy run '(?s)(.*)' 'hello\nworld'
captures: 0:[0..12] "hello\nworld" 1:[0..12] "hello\nworld"