use File::Copy qw();
if (-f "Normalize.xs") {
    print STDERR "Disabling XS in sources...\n";
    die "***** Failed, sources could be inconsistent! *****\n"
     unless File::Copy::move('MANIFEST',        'MANIFEST.X')
        and File::Copy::move('MANIFEST.N',      'MANIFEST')
        and File::Copy::move('Normalize.pm',    'Normalize.pmX')
        and File::Copy::move('Normalize.xs',    'Normalize.xsX')
        and File::Copy::move('Normalize.pmN',   'Normalize.pm');
}