yes, it's quite new, but OTOH, it's in version App::Cpan 1.57 which is from december 2009.
I just knew about the option because I was one of the people who requested this feature. Unfortunately I don't see it in the changelog so I don't know in which version it was introduced.

update: s/App::cpan/App::Cpan/ (although the linked cpan search is case insensitive, but anonymous monk complained)