This example would (implicitly) put all available tiddlers into the pipe.
The first operator ``tag[task]`` would only pass tiddlers which are tagged with "task".
The ``!tag[done]`` operator is negated and only passes tiddlers which are not tagged with "done".
The last filter operator passes only tiddlers with a field "interesting" set to "very".
So as a result this filter would be used to obtain all tiddlers which are marked as task, aren't already done and are very interesting.
There are many filter operators already build into the core plug-in including the mentioned tag- and field operators, filter operators to sort the tiddlerlist by a specified field, etc.
But more sophisticated operators are possible, too.
An example would be the search-operator. This filter operator looks for the searched string in the text and in the tags of the tiddlers.
If the provided filter operators are not enough, a developer can add new filters by adding a module with the ``filteroperator`` type.