use XML::Twig;
my $outfile = 'extra.snp';
open my $out,'>',$outfile or die "Could not open file '$outfile' $!";
my $file = shift @ARGV;	#the file to parse
my $twig = XML::Twig->new
(
twig_handlers => 
	{
		'Rs' => \&rsId,
		'Rs' => \&snpType,
		'Rs' => \&snpClass,
        'Rs/Sequence/Observed' => \&Observed,
		'Rs/Sequence/Seq3' => \&Seq3,
		'Rs/Sequence/Seq5' => \&Seq5,
    }
);
    $twig -> parsefile( "$file");
sub rsId 
	{
        my ($twig, $elt) = @_;
        print $out $elt->att('rsId'), "\n";
    }         
sub snpType 
	{
        my ($twig, $elt) = @_;
        print $out $elt->att('snpType'), "\n";
    }   
sub snpClass 
	{
        my ($twig, $elt) = @_;
        print $out $elt->att('snpClass'), "\n";
    }         
sub Observed 
	{
        my ($twig, $elt) = @_;
        print $out $elt->text, "\t";
    }
sub Seq5 {
        my ($twig, $elt) = @_;
        print $out substr($elt->text, -30,30), "\t";
    }
sub Seq3 {
        my ($twig, $elt) = @_;
        print $out substr($elt->text, 0,30), "\t";
    }

##</code><code>##

<?xml version="1.0" encoding="UTF-8"?>
<ExchangeSet xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http:/
/www.ncbi.nlm.nih.gov/SNP/docsum" xsi:schemaLocation="http://www.ncbi.nlm.nih.go
v/SNP/docsum ftp://ftp.ncbi.nlm.nih.gov/snp/specs/docsum_3.4.xsd" specVersion="3
.4" dbSnpBuild="144" generated="2015-05-26 09:54">
    <SourceDatabase taxId="9606" organism="human" gpipeOrgAbbr="hs"/>
    <Rs rsId="3894" snpClass="snp" snpType="notwithdrawn" molType="genomic" genotype="true" bitField="050028000005130500030100" taxId="9606">
        <Het type="est" value="0.05" stdError="0.1547"/>
        <Validation byCluster="true" byOtherPop="true" byHapMap="true" by1000G="
true">
            <otherPopBatchId>7179</otherPopBatchId>
        </Validation>
        <Create build="36" date="2000-09-19 17:02"/>
        <Update build="144" date="2015-05-07 10:52"/>
        <Sequence exemplarSs="491581208" ancestralAllele="C,C">
            <Seq5>ATAAGCAAATAACTGAAGTTTAATCAGTCTCCTCCCAGCAAGTGATATGCAACTGAGATTCC
TTATGACACATCTGAACACTAGTGGATTTGCTTTGTAGTAGGAACAAGGTACATTCGCGGGATAAATGTGGCCAAGTTTT
ATCTGCTGCCAGGGCTTTCAAATAGGTTGACCTGACAATGGGTCACCTCTGGGACTGA</Seq5>
            <Observed>C/T</Observed>
            <Seq3>AATTAGGAAGAGCTGGTACCTAAAATGAAAGATGCCCTTAAATTTCAGATTCACAATTTTTT
TTTCTTAGTATAAGCATGTCCCATGTAATATCTGGGATATACTCATACCTTTAAAAATGTGCTCATTGTTTATCTGAAAT
TCACATTTTAACAGGGAACCATTGTTTTGTTATTGTTTATTGTTTTGTTTCTAAATAA</Seq3>
        </Sequence>