Helo again! Everything works normal now. My code is:

#!/usr/bin/perl

# use module
use XML::Simple;
use Data::Dumper;

# create object
$xml = new XML::Simple (KeyAttr=>[]);

#read XML file
$data = $xml->XMLin("data.xml");

#dereference hash ref

#print Dumper($data);
print $data->{PMID}, "\n";
print $data->{Article}->{ArticleTitle}, "\n";

foreach $e (@{$data->{Article}->{AuthorList}->{Author}})
{
    $authors.= $e->{LastName}." ".$e->{Initials}.', ';
}

print $data->{Article}->{Journal}->{ISOAbbreviation}, " ";
print $data->{Article}->{Journal}->{JournalIssue}->{PubDate}->{Year}, 
+";", ;
print $data->{Article}->{Journal}->{JournalIssue}->{Volume}, ":";
print $data->{Article}->{Pagination}->{MedlinePgn}, "." ;
print "\n";
[download]

and gets all the details I need. BUT there is a problem when I try to put 2 XMLs together, like:

<?xml version='1.0'?>
<PubmedArticle>
            <PMID>1766380</PMID>
            <Article PubModel="Print">
                <Journal>
                    <JournalIssue CitedMedium="Print">
                        <Volume>5</Volume>
                        <Issue>9</Issue>
                        <PubDate>
                            <Year>1991</Year>
                            <Month>Sep</Month>
                        </PubDate>
                    </JournalIssue>
                   <ISOAbbreviation>Mol. Microbiol.</ISOAbbreviation>
                </Journal>
                <ArticleTitle>PhoP/PhoQ: macrophage-specific modulator
+s of Salmonella virulence?</ArticleTitle>
                <Pagination>
                    <MedlinePgn>2073-8</MedlinePgn>
                </Pagination>
                <AuthorList CompleteYN="Y">
                    <Author ValidYN="Y">
                        <LastName>Miller</LastName>
                        <ForeName>S I</ForeName>
                        <Initials>SI</Initials>
                    </Author>
                    <Author ValidYN="Y">
                        <LastName>Tsirigos</LastName>
                        <ForeName>K T</ForeName>
                        <Initials>KT</Initials>
                    </Author>
                    <Author ValidYN="Y">
                        <LastName>Dinous</LastName>
                        <ForeName>A E</ForeName>
                        <Initials>AE</Initials>
                    </Author>                    
                </AuthorList>
             </Article>
</PubmedArticle>  
<PubmedArticle>
        <MedlineCitation Owner="NLM" Status="MEDLINE">
            <PMID>16039843</PMID>
            <DateCreated>
                <Year>2005</Year>
                <Month>08</Month>
                <Day>01</Day>
            </DateCreated>
            <DateCompleted>
                <Year>2005</Year>
                <Month>12</Month>
                <Day>08</Day>
            </DateCompleted>
            <DateRevised>
                <Year>2006</Year>
                <Month>11</Month>
                <Day>15</Day>
            </DateRevised>
            <Article PubModel="Print">
                <Journal>
                    <ISSN IssnType="Print">0959-440X</ISSN>
                    <JournalIssue CitedMedium="Print">
                        <Volume>15</Volume>
                        <Issue>4</Issue>
                        <PubDate>
                            <Year>2005</Year>
                            <Month>Aug</Month>
                        </PubDate>
                    </JournalIssue>
                    <Title>Current opinion in structural biology</Titl
+e>
                    <ISOAbbreviation>Curr. Opin. Struct. Biol.</ISOAbb
+reviation>
                </Journal>
                <ArticleTitle>TonB-dependent outer membrane transport:
+ going for Baroque?</ArticleTitle>
                <Pagination>
                    <MedlinePgn>394-400</MedlinePgn>
                </Pagination>
                <Abstract>
                    <AbstractText>The import of essential organometall
+ic micronutrients (such as iron-siderophores and vitamin B(12)) acros
+s the outer membrane of Gram-negative bacteria proceeds via TonB-depe
+ndent outer membrane transporters (TBDTs). The TBDT couples to the To
+nB protein, which is part of a multiprotein complex in the plasma (in
+ner) membrane. Five crystal structures of TBDTs illustrate clearly th
+e architecture of the protein in energy-independent substrate-free an
+d substrate-bound states. In each of the TBDT structures, an N-termin
+al hatch (or plug or cork) domain occludes the lumen of a 22-stranded
+ beta barrel. The manner by which substrate passes through the transp
+orter (the "hatch-barrel problem") is currently unknown. Solution NMR
+ and X-ray crystallographic structures of various TonB domains indica
+te a striking structural plasticity of this protein. Thermodynamic, b
+iochemical and bacteriological studies of TonB and TBDTs indicate fur
+ther that existing structures do not yet capture critical energy-depe
+ndent and in vivo conformations of the transport cycle. The reconcili
+ation of structural and non-structural experimental data, and the una
+mbiguous experimental elucidation of a detailed molecular mechanism o
+f transport are current challenges for this field.</AbstractText>
                </Abstract>
                <Affiliation>Department of Molecular Physiology and Bi
+ological Physics, University of Virginia, PO Box 800736, Charlottesvi
+lle, VA 22908-0736, USA. mwiener@virginia.edu</Affiliation>
                <AuthorList CompleteYN="Y">
                    <Author ValidYN="Y">
                        <LastName>Wiener</LastName>
                        <ForeName>Michael C</ForeName>
                        <Initials>MC</Initials>
                    </Author>
                </AuthorList>
                <Language>eng</Language>
                <GrantList CompleteYN="Y">
                    <Grant>
                        <GrantID>DK 59999</GrantID>
                        <Acronym>DK</Acronym>
                        <Agency>NIDDK</Agency>
                    </Grant>
                </GrantList>
                <PublicationTypeList>
                    <PublicationType>Journal Article</PublicationType>
                    <PublicationType>Research Support, N.I.H., Extramu
+ral</PublicationType>
                    <PublicationType>Research Support, U.S. Gov't, P.H
+.S.</PublicationType>
                    <PublicationType>Review</PublicationType>
                </PublicationTypeList>
            </Article>
            <MedlineJournalInfo>
                <Country>England</Country>
                <MedlineTA>Curr Opin Struct Biol</MedlineTA>
                <NlmUniqueID>9107784</NlmUniqueID>
            </MedlineJournalInfo>
            <ChemicalList>
                <Chemical>
                    <RegistryNumber>0</RegistryNumber>
                    <NameOfSubstance>Bacterial Outer Membrane Proteins
+</NameOfSubstance>
                </Chemical>
                <Chemical>
                    <RegistryNumber>0</RegistryNumber>
                    <NameOfSubstance>Bacterial Proteins</NameOfSubstan
+ce>
                </Chemical>
                <Chemical>
                    <RegistryNumber>0</RegistryNumber>
                    <NameOfSubstance>Membrane Proteins</NameOfSubstanc
+e>
                </Chemical>
                <Chemical>
                    <RegistryNumber>0</RegistryNumber>
                    <NameOfSubstance>Multiprotein Complexes</NameOfSub
+stance>
                </Chemical>
                <Chemical>
                    <RegistryNumber>0</RegistryNumber>
                    <NameOfSubstance>tonB protein, Bacteria</NameOfSub
+stance>
                </Chemical>
            </ChemicalList>
            <CitationSubset>IM</CitationSubset>
            <MeshHeadingList>
                <MeshHeading>
                    <DescriptorName MajorTopicYN="Y">Bacterial Outer M
+embrane Proteins</DescriptorName>
                    <QualifierName MajorTopicYN="N">chemistry</Qualifi
+erName>
                    <QualifierName MajorTopicYN="N">metabolism</Qualif
+ierName>
                </MeshHeading>
                <MeshHeading>
                    <DescriptorName MajorTopicYN="Y">Bacterial Protein
+s</DescriptorName>
                    <QualifierName MajorTopicYN="N">chemistry</Qualifi
+erName>
                    <QualifierName MajorTopicYN="N">metabolism</Qualif
+ierName>
                </MeshHeading>
                <MeshHeading>
                    <DescriptorName MajorTopicYN="N">Biological Transp
+ort</DescriptorName>
                    <QualifierName MajorTopicYN="N">physiology</Qualif
+ierName>
                </MeshHeading>
                <MeshHeading>
                    <DescriptorName MajorTopicYN="N">Crystallography, 
+X-Ray</DescriptorName>
                </MeshHeading>
                <MeshHeading>
                    <DescriptorName MajorTopicYN="Y">Membrane Proteins
+</DescriptorName>
                    <QualifierName MajorTopicYN="N">chemistry</Qualifi
+erName>
                    <QualifierName MajorTopicYN="N">metabolism</Qualif
+ierName>
                </MeshHeading>
                <MeshHeading>
                    <DescriptorName MajorTopicYN="N">Models, Molecular
+</DescriptorName>
                </MeshHeading>
                <MeshHeading>
                    <DescriptorName MajorTopicYN="N">Multiprotein Comp
+lexes</DescriptorName>
                </MeshHeading>
                <MeshHeading>
                    <DescriptorName MajorTopicYN="Y">Protein Conformat
+ion</DescriptorName>
                </MeshHeading>
            </MeshHeadingList>
            <NumberOfReferences>38</NumberOfReferences>
        </MedlineCitation>
        <PubmedData>
            <History>
                <PubMedPubDate PubStatus="received">
                    <Year>2005</Year>
                    <Month>6</Month>
                    <Day>7</Day>
                </PubMedPubDate>
                <PubMedPubDate PubStatus="revised">
                    <Year>2005</Year>
                    <Month>6</Month>
                    <Day>18</Day>
                </PubMedPubDate>
                <PubMedPubDate PubStatus="accepted">
                    <Year>2005</Year>
                    <Month>7</Month>
                    <Day>8</Day>
                </PubMedPubDate>
                <PubMedPubDate PubStatus="pubmed">
                    <Year>2005</Year>
                    <Month>7</Month>
                    <Day>26</Day>
                    <Hour>9</Hour>
                    <Minute>0</Minute>
                </PubMedPubDate>
                <PubMedPubDate PubStatus="medline">
                    <Year>2005</Year>
                    <Month>12</Month>
                    <Day>13</Day>
                    <Hour>9</Hour>
                    <Minute>0</Minute>
                </PubMedPubDate>
            </History>
            <PublicationStatus>ppublish</PublicationStatus>
            <ArticleIdList>
                <ArticleId IdType="pii">S0959-440X(05)00124-7</Article
+Id>
                <ArticleId IdType="doi">10.1016/j.sbi.2005.07.001</Art
+icleId>
                <ArticleId IdType="pubmed">16039843</ArticleId>
            </ArticleIdList>
        </PubmedData>
    </PubmedArticle>
[download]

I get the error Only Comments, PIs and whitespace allowed at end of document [Ln: 40, Col: 1]
Line 40 is the line when the other </PubmedArticle> element begins... Do I have any mistake?