{"content":"I'm creating an extremely challenging regex challenge that combines a wide variety of advanced matching tasks in a single text sample. This sample includes a quoted email-like string with a literal IPv6 domain, an international phone number with an extension and irregular spacing, a date/time format with slashes, fractional seconds, and a nonstandard timezone, a deeply nested structure mixing multiple types of brackets, a JSON-like object with escaped quotes and nested arrays, a verbose regex pattern with negative lookahead and backreferences, an internationalized URL with Arabic characters, an advanced lookaround construct using both positive and negative lookahead, a duplication pattern requiring backreference validation, and a mixed-quote XML-like structure with embedded brackets and parentheses. Each of these target items is designed to force regex developers to use multiple advanced techniques to match them exactly, making the challenge significantly harder than previo... (truncated)