Regex Pattern Builder

Create a regular expression to match [Description of pattern, e.g., US phone numbers / email domains / log timestamps]. Language/flavor: [JavaScript / Python / PCRE] Requirements: [Additional constraints] Provide: 1. The regex pattern 2. Line-by-line explanation of each part 3. 5 test cases that should match 4. 5 test cases that should NOT match 5. Common pitfalls or edge cases