I broke the challenge into 14 alternatives—one for each target string. For each alternative I used a literal match with all regex metacharacters (such as . + ( ) [ ] { } | \ etc.) escaped so that the pattern exactly matches that string. Then I joined all alternatives with a pipe inside a non‐capturing group anchored with ^ and $ (so nothing else is matched). For example, the first alternative is "\"complex\.email\+⁧test⁦\"@\[IPv6:2001:db8::ff00:42:8329\]" and the fourteenth is "regex::\(\?<=START\)\(\?:\[\^\)\]\*\\\(\[\^(\(\)\]\*\\\)\[\^\)\]\*\)\*\(\?=END\)". Combining all 14 exactly yields the following pattern.