I also had a need for Google Desktop-like tool on Linux. You could build your own using swish-e or Xapian which both have perl-friendly API.

But you don't need to. For almost a year, there is great personal search engine called Estraier which I'm testing for a while and I'm impressed.

It has vector model, clustering of results and many filter scripts for input format (doc, xls, ppt, etc..). Output is friendly to parsing (there is special command which produce XML output), and even includes cgi script which can merge multiple indexes into single search (for example your e-mail and documents which are in separate index files). Writing perl to exercise indexer is left as a exercise to YAPH.