Hi,

xpath is easy with xpather.pl

use XML::LibXML;
my $dom = XML::LibXML->new(qw/ recover 2 /)->load_xml(  IO => $in );

for my $key ( $dom->findnodes( q{  /drug/* } ) ){
    print $key->nodeName, "\n", 
          $key->nodePath, "\n",
          $key->textValue, "###\n";
}
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If /drug doesn't work then  *[local-name()='drug' ] will

Or even /x:drug if you use sub XML::LibXML::Node::F