I built a pattern that matches exactly one of the 16 target items by listing each one as an alternative with all regex metacharacters escaped as needed. For example, dots (.) are escaped as \., plus signs as \+, parentheses as \( or \), square brackets as \[ or \], curly braces as \{ or \}, forward slashes as \/, and backslashes as \\ when needed. This ensures that only the exact characters of each target string will match and nothing else. Note that no extra anchors or flags are used so that the regex exactly matches any one of these items when found in the challenge text.