{"content":"I'm creating an extremely difficult challenge that pushes regex techniques to the limit. This challenge integrates a mix of advanced pattern types: an email address with a quoted local part and an IPv6 domain; an international phone number including an optional area code and extension; ISO8601 date-time formats with varying separators and milliseconds; nested and balanced grouping with mixed delimiters; product codes with Greek characters; version strings with pre-release and build metadata; a string containing a hash separator; an XML tag with mixed quoting in attributes; a function expression with Greek symbols; a nested bracket structure; a mathematical expression with an integral and infinity symbols; an internationalized URL containing non-ASCII characters; and finally, a literal string that includes a number of regex metacharacters. Each target item must be matched exactly, challenging even the most seasoned regex experts to handle proper escaping, grouping, alternati... (truncated)