There are three implementations. Each uses the IIPC's jwarc library for parsing WARC files. They differ only in the regular expression engine that is used - the default one that ships with the JDK, Google's re2j, and Anders Møller's dk.brics.automaton library.
./go JDK # Use the JDK's engine ./go Brics # Use the Brics engine ./go Re2j # Use the Re2j engine
You can optionally provide your own WARC file to be searched as a second argument.