Regex Tester & Validator

Matches palindromic strings up to 11 characters long by capturing the first five characters in optional groups, optionally consuming a middle character, then requiring the captured characters to repeat in reverse order via backreferences. Since each capture group (.?) matches at most one character, strings longer than 11 characters cannot be validated. Often used in interview challenges or code golf to demonstrate the limits of regular expressions, as true arbitrary-length palindrome matching is impossible with regex.