You could reinvoke String::Approx using successively more and more relaxed constraints until it gets some hits. Those hits would then be all equally "the best", unless you have some other criterion in mind. For example, if given "abcd" and the best matches are "abce" or "bbcd", there's no one match that's "best". Perhaps you need to rethink your problem.

-- Randal L. Schwartz, Perl hacker