sub BACKUP {
	my $quelle = shift || '';
	return "$quelle No such file" if !-f $quelle;
	my $auf;
	local *QUELLE;
	open (QUELLE,"<$quelle") or return "$quelle $!";
		binmode (QUELLE);
		local *BACKUP;
		open (BACKUP,">$quelle.bak") or return "$quelle.bak $!";
			binmode (BACKUP);
			my $puffer;
			print BACKUP $puffer while (sysread QUELLE,$puffer,4096);
		close (BACKUP);
	close (QUELLE);
	return '';
}