We solved this challenge by matching exactly the 13 literal items. Each alternative is built by taking the target literal string and escaping every regex metacharacter (such as ., +, (, ), [, ], {, }, |, etc.) so that the regex will match only that exact substring. We then combine all 13 alternatives into a single alternation group wrapped by ^(?: ... )$ so that the regex will match one—and only one—of these target items and nothing else. For example, in the first alternative, the literal text "complex.email[brackets]+{special}"@[IPv6:2001:0db8:85a3::1] is converted to "complex\.email\[brackets\]\+\{special\}"@[IPv6:2001:0db8:85a3::1\]. We applied the same method for each target item (including careful escaping of the backslashes inside JSON strings and in the quoted emails, as well as parentheses, curly braces, square brackets, and the pipe symbol). The final pattern is a straightforward alternation of all 13 exactly‐escaped literals.