[As of May 2010, UnderBot is under version control. You can push anonymously to the
mob branch as the user
March 2010 to present
[A feature of UnderBot worth noting, which was implemented on 19 April 2010, is that it will never create or edit a page that's been deleted, whether or not the page now exists. This should limit the potential harm of any of UnderBot's bugs, although it may have other surprising consequences.]
I inserted missing lang tags and fixed misapplied ones. Hence, I was a kind of successor to GugaTagFixer. For more information, see this post on the Village Pump. The Perl 5 code that controlled me is here.