tried using XML::LibXML as well but I can't get it to return a valid data structure
You can use XML::LibXML but because of the xmlns="http://xmlns.sony.net..." in the TMSMessage tag you have to perform some namespace trickery. By referring to this node I came up with this snippet which may be of help: 
my $text = q|<?xml version="1.0" encoding="UTF-8"?>
<TMSMessage xmlns="http://xmlns.sony.net/d-cinema/tms-api/v1">
<MessageHeader>
<Id>-1</Id>
<Type>ListPerformances</Type>
...etc
</TMSMessage>|;

my $doc = XML::LibXML->load_xml(string => $text);
my $xc = XML::LibXML::XPathContext->new( $doc->documentElement() );
$xc->registerNs( pfx => 'http://xmlns.sony.net/d-cinema/tms-api/v1' );

my @events = $xc->findnodes('//pfx:EventInfo');
for my $event (@events) {
    my $id = $xc->findvalue('pfx:EventId', $event);
    print "EventId: $id\n";
    my @packs = $xc->findnodes('pfx:PreshowPackList/pfx:PreshowPack', 
+$event);
    if ( not @packs ) {
        print "No Packs\n";
        next;
    }
    for my $pack (@packs) {
        my $pack_id = $xc->findvalue('pfx:PackId', $pack) || "No PackI
+d";
        print "PackId: $pack_id\n";
    }
}

[download]
Output using your sample XML: 
EventId: 2015060400000157
No Packs
EventId: 2015060400000164
No Packs
EventId: 2015060200000562
PackId: b863a576-d8a3-4f5d-92a7-b66f876f6d7c
PackId: No PackId
PackId: a55164d0-faa7-4c7c-a688-ed36011add95
EventId: 2015060200000563
PackId: 760eb073-81f8-45cb-8553-484c5cecb740
PackId: No PackId
PackId: a55164d0-faa7-4c7c-a688-ed36011add95

[download]

In reply to Re: XML Parsing Problems by tangent
in thread XML Parsing Problems by taralon

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