calculate-overlay/profiles/base/package.use/exactly-one-of

# smp? ( exactly-one-of ( kaapi tbb ) )
sci-libs/vtk tbb

# exactly-one-of ( alsa oss portaudio pulseaudio )
app-accessibility/julius -pulseaudio

#exactly-one-of ( qt4 qt5 )
x11-terms/qterminal qt5
x11-libs/qtermwidget qt5

# hcache? ( exactly-one-of ( berkdb gdbm lmdb qdbm tokyocabinet )
mail-client/mutt -gdbm

# exactly-one-of ( expat xml )
media-libs/libmetalink expat

# exactly-one-of ( openssl nss gnutls )
net-fs/s3fs openssl