perl-String-Similarity

The similarity-function calculates the similarity index of its two
arguments. A value of 0 means that the strings are entirely different.
A value of 1 means that the strings are identical. Everything else
lies between 0 and 1 and describes the amount of similarity between
the strings.

It roughly works by looking at the smallest number of edits to change
one string into the other.

You can add an optional argument $limit (default 0) that gives the
minimum similarity the two strings must satisfy. similarity stops
analyzing the string as soon as the result drops below the given limit,
in which case the result will be invalid but lower than the given
$limit. You can use this to speed up the common case of searching for
the most similar string from a set by specifing the maximum similarity
found so far.