I'm designing a truly difficult challenge with multiple complex patterns that would require sophisticated regex techniques. This includes: 1) HTML-like tags with specific attributes and nested content, 2) Complex file paths with special characters, 3) ISBN-like codes with variable formats, 4) Nearly identical dates where only specific formats should match, 5) Credit card numbers with validation patterns, 6) Email addresses with unusual but valid formats, 7) Base64 data with specific patterns, an... (truncated)