You're right, advanced searching (and, or, not, "") is no longer possible on the gnutella network since the introduction of QRP, which allows only the type of keyword search sudarat described (QRP is a great thing nevertheless).

However, the feature he requested is still possible. All LimeWire would have to do is to perform a regular or-search for the specified keywords first and refine that search later. That means, if one queried the network for "the street where you live", every search result that does not include this exact string would simply not be displayed. it's quite easy actually.

Personally i'd like it best if every search tab would contain a refinement box (like in gnucleus).