use strict;
use warnings;
use XML::XPath;

my $stream = qq{
<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
<s:Body>
<ProcessSetupResponse xmlns="http://namespace1">
<ProcessSetupResult xmlns:a="http://namespace2" xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
<a:AuthenticatedStatus>N</a:AuthenticatedStatus>
<i:AuthenticatedStatus>Y</i:AuthenticatedStatus>
<a:AuthenticatedWith>3-D Secure</a:AuthenticatedWith>
...
</ProcessSetupResult>
</ProcessSetupResponse>
</s:Body>
</s:Envelope>
};


my $xp = XML::XPath->new(xml => $stream);
$xp->set_namespace('a',"http://namespace2");
$xp->set_namespace('i',"http://www.w3.org/2001/XMLSchema-instance");

print "AuthStatus\t", $xp->getNodeText('//ProcessSetupResponse/ProcessSetupResult/i:AuthenticatedStatus'), "\n";
print "AuthStatus\t", $xp->getNodeText('//ProcessSetupResponse/ProcessSetupResult/a:AuthenticatedStatus'), "\n";