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

my $xp = XML::XPath->new(ioref => *DATA);

print $xp->findnodes_as_string('/child::ZED_INVOIC02_CRG/child::IDOC/
                                child::E1EDK02/following::E1EDK02');

__DATA__
<ZED_INVOIC02_CRG>
  <IDOC BEGIN="1">
    <E1EDK02 SEGMENT="1">
      <QUALF>009</QUALF>
    </E1EDK02>
    <E1EDK02 SEGMENT="1">
      <QUALF>020</QUALF>
    </E1EDK02>
    <E1EDK02 SEGMENT="1">
      <QUALF>900</QUALF>
    </E1EDK02>
  </IDOC>
</ZED_INVOIC02_CRG>