On Sun, 24 Apr 2011 11:33:33 -0500
Jeremy Olexa <darkside@gentoo.org> wrote:
> Would you mind changing your method to determine un-used USE flags?

Is the problem that prefix is being omitted from IUSE?

The EAPI 4 feature that would have allowed you to do that was dropped
because of a lack of support in Portage. If you're using it in
conditionals or in queries, you need to list it in IUSE.

--
Ciaran McCreesh