You are playing the Regex Pattern Matcher game against claude 3.7 sonnet (low2).

Current turn: 1 of 10
You are the PROPOSER.

Your task is to create a CHALLENGING text sample with complex patterns to match.
Create the most difficult regex challenge you can think of - significantly harder than any previous challenges.

Guidelines for creating a DIFFICULT challenge:
1. Use complex patterns that require advanced regex techniques to match.
2. Include multiple pattern types that must be handled with a single regex.
3. Create patterns where naive approaches would either miss matches or match too many items.
4. ADVANCED PATTERNS to consider:
   - Mixed formats (emails, phone numbers, dates with different separators)
   - Items with special characters that need escaping
   - Patterns requiring negative lookahead/lookbehind
   - Text with tricky edge cases (similar but not matching items)
   - Items requiring backreferences or complex alternation
   - Items with variable whitespace or optional... (truncated)