grex is a library as well as a command-line utility that is meant to simplify the often complicated and tedious task of creating regular expressions. It does so by automatically generating a single regular expression from user-provided test cases. The resulting expression is guaranteed to match the test cases which it was generated from.

Unfortunately, the tool’s authors still think you need learn how to write regexes, even when grex works flawlessly (and I tend to agree with them).