pre_upgrade() {
  if(test `vercmp '3.4.3-5' "$2"` -ge 0); then
    mv /usr/share/nethack /tmp/nethack-backup
  fi
}

post_upgrade() {
  if(test `vercmp '3.4.3-5' "$2"` -ge 0); then
    rm -rf /var/games/nethack
    mv /tmp/nethack-backup /var/games/nethack
  fi
}