Your example is clear but not "real".
My Regular Expression Short Answer question type plugin is indeed not part of standard Moodle and needs to be installed by an admin. In the meantime you can have a look at the documentation here: https://docs.moodle.org/310/en/Regular_Expression_Short-Answer_question_type and decide for yourself whether it would fit the bill.
Especially Example 4.The 'permutation' feature.