undef $/;
open(IN,"<sample.xml") || die "can not open the input xml file";
open(OUT,">sample_out.xml") || die "can not open the out xml file";
$str=<IN>;
close IN;
$headera="";
$headerb="";
$footer="</bibdataset>";
$has=();
$headera=$& if ($str =~ /<\?xml.*\?>/si);
$headerb=$& if ($str =~ /<bibdataset[^>]+>/si);
while ($str =~ /<item>.*?<\/item>/gsi) {
	$con=$&;
       if ($con =~ /<itemid\s+idtype\s*=\s*\"PUI\">\s*(\d+)\s*<\/itemid>/)
	{
		$puino=$1;
		$has{$puino}=$con;
	}
}
print OUT $headera;
print OUT $headerb;

foreach  $ke(sort keys %has) {
print OUT $has{$ke};
}

print OUT $footer;
close OUT;