Unfortunately the output is terrible - both unusable in your code and unusable to learn from.
I agree. It's a clever hack, but instead of spending the time learning how to use this and then using it for all of your regular expressions, you could just learn regular expressions yourself. It's as simple as learning the syntax and then keeping a handy bookmark to some of the less-commonly used special characters, in addition to plenty of practice.
UI needs work, as it seems a bit busy, but otherwise seems fine enough.
Am the only one who thinks this app is pretty hard to use?
<3 Regular expressions have always been one of my problems!