// include the latest version of the regex crate in your Cargo.toml
extern crate regex;
use regex::Regex;
fn main() {
  let regex = Regex::new(r"(?ms)<!--(?!\s*(?:\[if [^\]]+]|<!|>))(?:(?!-->)(.|\n))*-->").unwrap();
  let string = "<!-- some comments 1 -->
<!-- 1.91 -->
<!--
//-->
<!-- -->
<!--[if IE]> <![endif]-->
<!--[if !IE]><!-->  <!--<![endif]-->
<!--[if IE 6]> <![endif]-->";
  
  // result will be a tuple containing the start and end indices for the first match in the string
  let result = regex.captures(string);
  
  let (start, end) = match result {
    Some((s, e)) => (s, e),
    None => {
        // ...
    }
  };
  
  
  println!("{}", &string[start, end]);
}
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Rust, please visit: https://docs.rs/regex/latest/regex/