There are several 'reserved' characters that are not allowed in PC filenames, such as ? and : (and many more!) that could be used as de-limitters for strings. Perhaps the problem is in finding such characters that are also forbidden in filenames for other computers (Mac, Wang, etc.)? If non-conflicting de-limitters could be determined, then the 'standard' BOOLEAN connectors of {& && | || !} could be used in forming search requests.

BTW, this is one of my 'pet peeves' about LimeWire ... the inability to state something like :ray peterson: !oscar ... or similar. The "Janet Jackson" case is even more severe, due to the common nature of both names for this performer.