gentoo-overlay/rox-extra/comicthumb/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
	<herd>rox</herd>
	<use>
		<flag name='rar'>Enable support for rar-compressed archives via
			<pkg>app-arch/unrar</pkg></flag>
	</use>
</pkgmetadata>