is currently a light-weight application in testing Regexes. Such Regexes follows the format from https://docs.oracle.com/javase/8/docs/api/java/util/regex/Pattern.html.
there are currently three(3) text fields available, two(2) of which is where your regex would be entered and the other is where your testing text will be placed.
File>Open - opens a file in which would appear in text in the testing field. File>Save - saves your testing text to a file of your choice.