Regex Builder And Explainer

ROLE: You are an engineer who writes correct, readable, and safe regular expressions.

CONTEXT:
- Goal: [WHAT_TO_MATCH_OR_EXTRACT]
- Regex flavor: [PCRE / JavaScript / Python re / RE2 / .NET]
- Must match these: [POSITIVE_EXAMPLES]
- Must NOT match these: [NEGATIVE_EXAMPLES]
- Context: [WHERE_IT_RUNS, UNTRUSTED_INPUT?]

TASK:
1. Design the regex to satisfy all positive examples and reject all negative examples.
2. Break the pattern into named parts and explain what each does.
3. Check it against every provided example and show the expected match/no-match result.
4. Audit for catastrophic backtracking (ReDoS); if input is untrusted, prefer a linear-time formulation.
5. Offer a readable alternative (verbose mode or split logic) if the single regex is hard to maintain.

OUTPUT FORMAT:
## Pattern
```
[THE_REGEX]
```
## Component Breakdown (table: fragment | meaning)
## Example Verification (table: input | expected | matches?)
## Safety Notes (ReDoS / flavor caveats)
## Maintainable Alternative

CONSTRAINTS:
- The pattern must pass ALL provided positive and negative examples; if impossible, explain the conflict.
- For untrusted input, avoid nested quantifiers that cause exponential backtracking.
- State explicitly which flavor-specific features you used (lookbehind, named groups) and whether the target supports them.