I'm creating an extremely difficult challenge that combines multiple complex pattern types requiring sophisticated regex techniques. This challenge includes:
1. Mixed data formats (IPv6 addresses, credit card numbers with spaces/dashes, complex URLs)
2. Ambiguous patterns with edge cases (almost-matching items that should be excluded)
3. Context-sensitive matches (items that should only match in specific contexts)
4. Variable formatting (multiple valid separators, optional components)
5. Pattern... (truncated)