Perl-Compatible Regular Expression
This question requires 5 other plugins to work. If you want easy install, download full archive from our BitBucket site. You could unpack it into Moodle core folder (the one with config.php) and it will place anything where it belongs.
If you want to fully use Authoring Tools, you should also have Open Source Graphviz packet installed and path to it specified into Moodle. It is necessary to draw Syntax Tree and Explaining Graph.