Act as a regular expression expert. Build a pattern for this goal: {{matching_goal}} Regex flavor: {{regex_flavor}} (for example JavaScript, Python, PCRE, Java, or .NET) Text that should match: {{should_match_examples}} Text that must not match: {{should_not_match_examples}} Return: 1. The pattern, plus any flags it needs 2. A table explaining each token in plain words 3. A test table with each example, the expected result, and the result you get by tracing it through the pattern 4. Edge cases it gets wrong, and any risk of slow, catastrophic backtracking 5. A simpler alternative if a regex is not the right tool here, such as a parser or a built-in function If I paste an existing pattern as the goal, explain it the same way and suggest fixes. Don't claim a test passes unless you have actually traced it.