gentoo-overlay/sci-physics/cernlib-montecarlo/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
<herd>sci-physics</herd>
<longdescription lang="en">
  This metapackage provides various Monte Carlo libraries included in
  Cernlib (both shared and static). Likely only physicists will be
  interested in these packages.
  The libraries of Ariadne, Fritiof, Jetset, Lepto, and Pythia are not
  available for Gentoo: see cernlib Debian packaging for explanation.
</longdescription>
<use>
    <flag name="herwig">Build Herwig internal event generator, newer version
    available in <pkg>sci-physics/herwig</pkg></flag>
</use>
</pkgmetadata>