you cannot set the A variable in ebuilds, but the following ebuilds have: net-zope/zope/zope-2.4.0-r6.ebuild:A="Zope-${PV}-src.tgz ZEO-1.0b3.tgz" net-zope/zope/zope-2.5.1.ebuild:A="Zope-${PV}-src.tgz ZEO-1.0.tgz"
fixed in CVS.