The above example works by first checking if the input title has the field myfield and then using the Map Filter Run Prefix to replace the title with their value of that field. If the input tiddler does not have the field, an empty selection is returned. The subsequent Map Filter Run Prefix outputs an empty string when its run returns an empty selection (because the field is empty).

The above example demonstrates two different ways of accessing field values in filters: Use get when the title is not known in advance as with the Filter Filter Run Prefix where currentTiddler is set to the current input title. Use a TextReference as an indirect Filter Parameter when the title is known.