It's hard to be nice. It was developed 1989-1991 by Udi Manber and Sun Wu at the University of Arizona and many others. It is copyrighted by the University of Arizona, but free for non-commercial use. You can use many kinds of queries including arbitrary wild cards, sets of patterns, and in general, regular expressions.
Source code is available.
REXX is a programming language designed by Michael Cowlishaw of IBM UK Laboratories. Syntactically, REXX doesn't look that different from any other procedural language. Please take your time and visit the pages of my friend Robert Mahoney , who is the author of SpellGuard. Together with him, I am currently improving the multi-language version of SpellGuard. Please check regularly his page.