Is it possible to select on places using a non-match as well as a simple "contains" match?

I am thinking of the kind of conditional logic you can do with a LibreOffice spreadshseet, such as"does not contain" or "is null".  I have looked at the options for creating custom filters and I cannot find anything which seems to do this.

I see that there is a "Use regular expressions" check-box but I have tried all the representations I can think of for "empty string" and nothing seems to work, and I can't find any mention of the correct syntax to be used for regular expressions in any of the Gramps help pages.

The existing filters seem to work on the "contains" logic, because if you enter a place name of Hulme it also returns Davyhulme.

I know that I can work round it by sorting the data by a column, so if I am looking for addresses missing a postcode, say, I can see them at the top of the list, but I'd prefer to use the filters if it's possible.