Implementing approximate matching has been on my todo list for some time. I'm planning to either implement http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=5362... or http://www.sciencedirect.com/science/article/pii/S1570866704...

The data structure for the mealy recognizer described in the paper can very easily be changed to support minimal perfect hash numbers for all elements, without using more space (my implementation uses less space because of it, because the same information can be used to calculate the number of strings with a prefix in O(1) time).