Lucene is nice because it has a pretty well-defined plugin architecture where you can write a plugin which gets a parse tree, mutate the tree (to add fuzziness

Lucene is nice because it has a pretty well-defined plugin architecture where you can write a plugin which gets a parse tree, mutate the tree (to add fuzziness to the matching, for example), and then pass the tree to the next stage. It's a nicely composable way to extend functionality.