Strict code review that ignores style
codingReviews a diff for correctness, edge cases, and regressions — and refuses to comment on formatting.
Regex from examples, with the failing cases
Builds a pattern from positive examples and then states what it will wrongly match.
When to use it
You have a list of strings that should match and need to know what else will.
The prompt
Copy into your assistant
Write a regular expression that matches the following examples.
Then, before showing the pattern:
1. List the general form you inferred, including the edge cases the examples do not cover.
2. List at least three kinds of string that would match this pattern by accident.
3. State where the pattern is the wrong tool — nested structures, escaped quotes, anything not regular.
Only then output the pattern, with a one-line explanation per group.
Examples that should match:
<positive>
Examples that should not match:
<negative>
Flavour (PCRE, JS, Python):
<flavour>What to change
Always supply negatives. Without them the model writes a pattern that matches your examples and half of everything else.
Why it works
Item 3 is the honest part: it tells you when you need a parser instead, which is the answer more often than people want to hear.
More coding prompts
- Review an API design before you build itPressure-tests an endpoint spec for naming, pagination, errors, and the version you will regret in a year.
- A migration plan with a rollback you can actually runPlans a brownfield migration in steps small enough to revert, and names the point of no return.
- A test plan derived from a spec, not from the codeBuilds the test matrix from requirements and failure modes, so it catches what the implementation forgot.
Going deeper
- Debugging a server that will not startMCP servers · Level 2
- Writing a skill that changes behaviorSkills and prompts · Level 2
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