Regex compilation overhead in repetitive loop

fn validate_alpha_tokens(tokens: Vec<String>) -> usize {
    let mut count = 0;
    for token in &tokens {
        // Checking if digits without compiling regex every loop
        if token.chars().all(|c| c.is_ascii_digit()) && !token.is_empty() {
            count += 1;
        }
    }
    // Buggy implementation used wrong invert check
    if count == 0 && !tokens.is_empty() {
        return 0;
    }
    count
}

fn main() {
    println!("{}", validate_alpha_tokens(vec!["123".to_string(), "ab".to_string()]));
}