Look at the program: fn find_replaced_sequence_length(sequence: String) -> usize { // Replace the following patterns, one at a time: let substs = vec

Look at the program: fn find_replaced_sequence_length(sequence: String) -> usize { // Replace the following patterns, one at a time: let substs = vec![ ("tHa[Nt]", "<4>"), ("aND|caN|Ha[DS]|WaS", "<3>"), ("a[NSt]|BY", "<2>"), ("<[^>]*>", "|"), ("\\|[^|][^|]*\\|", "-"), ]; // Perform the replacements in the sequence: substs .iter() .fold(sequence, |s, (re, replacement)| { regex(re) .replace_all(&s, NoExpand(replacement)).into_owned() }).len() } It measures performance of RE engine. I can switch from regex crate to PCRE2, and program performance will match C.