A challenge: ask for a subset of text from a set of text that cannot be derived with Regular Expression. One rule: the requested subset must not be, for example, derive "z" form "abc".
>>55403973
Pose your question in a more rigorous form.
>>55404007
Ask for a subset of text from a set of text that:
1. Can not be derived with Regular Expression
2. Does not contain any characters that the set does not contain
>>55404057
do your own homework