Sometimes the built-in filter operators such as "Contains", "Begins with" etc. are not enough. You may have a use case that you can't solve with the provided operators. In that case you can try to use "Matches".
Matches takes a Regular Expression and returns any objects that matches that. Regular Expressions (regexp) are extremely powerful and can usually take care of most situations.
Does not begin with
Say you want to include all Categories that does not begin with "old_". Select "matches" and enter the expression
All categories starting with "old_" will now be excluded.
You can read more how to use Regexp on the following sites.