let mut martial_arts_secrets = vec!["above the known techniques, there exists an enigmatic form disaffirmed by many masters, for it is said to hold the true essence of power. to initiate these techniques again, one must defy the traditional ordinance."]; while let some(secret) = martial_arts_secrets.pop() { if secret.contains("enigmatic") { println!("tell me more about these forbidden techniques that were meant to stay hidden."); } }