   /// Checks if if all the characters in the string belong to a specific `CharacterSet`.
   ///
   /// - Parameter characterSet: The `CharacterSet` used to test the string.
-  /// - Returns: true if all the characters in the string belong to the `CharacterSet`, otherwise, false.
+  /// - Returns: *true* if all the characters in the string belong to the `CharacterSet`, otherwise false.
   public func containsCharacters(in characterSet: CharacterSet) -> Bool {
     guard !isEmpty else { return false }
     for scalar in unicodeScalars {

  ///
  /// - Parameters:
  ///   -  pattern:       Pattern to match.
  ///   - caseSensitive:  Search option: *true* for case-sensitive, *false* for case-insensitive. (if true this function is equivalent to `self.contains(...)`)
  ///
  ///  - Returns: true if contains match, otherwise false.
  public func contains(_ pattern: String, caseSensitive: Bool) -> Bool {
    if (caseSensitive) {
      return self.contains(pattern) //(self.range(of: pattern) != nil)

  
  /// **Mechanica**
  ///
  /// Returns *true* if `self` starts with a given prefix.
  public func starts(with prefix: String, caseSensitive: Bool = true) -> Bool {
    if !caseSensitive {
      return lowercased().hasPrefix(prefix.lowercased())
