It's called a minimal example. You can easily get nontrivial real-world versions, such as "All vowels or all uppercase" or "Three letters, at least two of which

It's called a minimal example. You can easily get nontrivial real-world versions, such as "All vowels or all uppercase" or "Three letters, at least two of which are A's". It is not reasonable to expect the user to manually disambiguate every regex.