I'm designing a challenge that combines multiple difficult regex concepts: 
1. Various URL formats with different protocols, subdomains, paths, and query parameters
2. Base64 encoded strings that need to be precisely identified
3. UUIDs in different formats (with/without dashes)
4. Credit card numbers with masked digits in different patterns
5. Complex version numbers with varying segments
6. ISBN-13 codes in multiple formats
7. Valid JSON snippets embedded in text

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