This Regex Generator site works as follows, you provide text examples by highlighting the strings to extract; the strings to not extract are the surrounding text. The Regex Generator finds out a regular expression that complies with provided examples and performs the desired text extraction task.

This is a research project of the Machine Learning Lab http://machinelearning.inginf.units.it/

The engine has also been released opensource here: https://github.com/MaLeLabTs/RegexGenerator