The indexing and searching of text based documents could be done with beagle (of which I've heard, but I have no experience with it). I guess you can write import filters for beagle's indexer.

Probably not perfect, but worth investigating.

A Perl module for building search engines is KinoSearch, which I successfully used for small projects (but which requires you to write a lot more code than an out-of-the-box solution like beagle).