Search mails using regular expressions

Hi,
I have already posted about this in the users mailing list but failed to get any useful info.
Are regular expressions currently available in Kmail? The ui interface both in filters and in the search dialog indicate that they are. I have done my best to determine this from the code by grepping for calls to QRegExp but this proved fruitless.
Can you advise whether the functionality is available and just broken or in fact that it is not supported.
If it is not currently supported is it likely to be added/restored in the future?
Best,
Colin Close