How to use regex crate in Rust regular expressions

Add the regex crate to your dependencies and use Regex::new to compile patterns, then call .replace_all or .is_match on your strings.

use regex::Regex;

let re = Regex::new(r"(?m)^ >").unwrap();
let fixed = re.replace_all(&input, ">");

For workspace projects like the Rust Book tools, define regex = "1.3.3" in [workspace.dependencies] and reference it with regex = { workspace = true } in your package's [dependencies].

The regex crate lets you find and replace text patterns in your Rust code. You define a pattern once, then use it to check if text matches or to swap out parts of a string. It's like using a search-and-replace tool that understands complex rules, such as finding lines that start with specific characters.