Email regex invalid

[frederikhors]

I'm trying to use the email regex from this SO thread:

use once_cell::sync::Lazy;
use regex::Regex;

static EMAIL_ADDRESS_REGEX: Lazy<Regex> = Lazy::new(|| {
    Regex::new(
        r"(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|"(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])*")@(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\[(?:(?:(2(5[0-5]|[0-4][0-9])|1[0-9][0-9]|[1-9]?[0-9]))\.){3}(?:(2(5[0-5]|[0-4][0-9])|1[0-9][0-9]|[1-9]?[0-9])|[a-z0-9-]*[a-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])+)\])",
    ).unwrap()
});

but I'm getting this error:

error: expected expression, found `?`
   |
11 | ...   r"(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|"(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\[\x01...
   |                                                                              ^ expected expression

Can you please help me?

[BurntSushi]

What you're seeing isn't a regex problem. It's a Rust syntax problem. The issue here is that your regex pattern contains a ". That needs to be escaped which you can't do in a raw string literal. Instead, you can make use of # in raw string literals. For example, you can write r#"foo"bar"#. Things like r##"foo"bar"## also work. You just have to balance the number of #.

Here's a link to working program: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=8bf265b6ee5f764582b94b9228cc3159