sub qx_cache {
    my $cmd = shift;

    my $cache = Cache::FileCache->new({ namespace => $0 });
    die 'no cache' if ! $cache;
    my $out = $cache->get( $cmd );
    if ( ! defined $out ) {
        $out = qx{ $cmd };
        $cache->set( $cmd, $out );
    }

    return $out;
}