I'm creating an extremely difficult challenge that combines multiple advanced regex concepts. This challenge involves:
1. IPv6 addresses in different formats (full, compressed with ::, and mixed notation)
2. Valid product codes with specific patterns and constraints
3. Credit card numbers with specific validation requirements
4. Items with intentional near-matches that should be excluded
5. Patterns requiring negative lookaround assertions
6. Strings that appear similar but have subtle differenc... (truncated)