I'm creating an exceptionally difficult challenge that combines:
1. Complex nested structures with varying depths and special characters
2. Custom data formats with conflicting similarities
3. Mathematical expressions with precise formats
4. URLs with specific query parameters and fragments
5. Mixed date-time formats with milliseconds and timezones
6. Items requiring careful negative lookaheads to avoid false matches
7. Patterns with tricky whitespace and optional components
8. Similar-looking p... (truncated)