It was removed because rubygems was made to be required by default so it was now...

		byroot 17 days ago \| parent \| context \| favorite \| on: Programmers and software developers lost the plot ... It was removed because rubygems was made to be required by default so it was now useless. The stdlib still contains `un.rb` though: https://github.com/ruby/ruby/blob/d428d086c23219090d68eb2d02...

Wow, I did not about un.rb. Looks cool though.