http://devmanual.gentoo.org/general-concepts/dependencies/index.html under Built with USE Dependencies, second list shows: app-misc/foo[!bar?] bar? (app-misc/foo ) !bar? ( app-misc/foo[-bar] ) there is a space missing after the first '(' before app-misc/foo.
betelgeuse@pena /mnt/checkouts/devmanual/trunk $ svn ci -m "Add space before parenthesis in dependency specifications. Fixes bug #286529. Thanks to grobian for reporting." Sending trunk/general-concepts/dependencies/text.xml Transmitting file data . Committed revision 154.