use strict;
use warnings;
use XML::Parser;

my $p1;
$p1 = new XML::Parser(
        Handlers => {
                Start => \&handle_start,
                End => \&handle_end,
                Proc => \&handle_proc
        });
my @stack;

$p1->parse(\*DATA);
if (@stack) {
  warn "stack not empty\n";
}

sub handle_start {
  my ($parser, $element) = @_;
  print "  " x scalar(@stack), "BEGIN $element\n";
  push(@stack, $element);
}

sub handle_end {
  my ($parser, $element) = @_;
  my $top = pop(@stack);
  print "  " x scalar(@stack), "END $element\n";
  unless ($element eq $top) {
    warn "expected $element, found $top\n";
  }
}

sub handle_proc {
  my ($parser, $target, $data) = @_;
  if ($target eq 'CLG.MDFO') {
    handle_start($parser, $target);
  } elsif ($target eq 'CLG.MDFC') {
    handle_end($parser, 'CLG.MDFO');
  }
}
__END__
<?CLG.MDFO ID="O001001M004000" IDREF="C001001M004000" ACTION="REPLACED" LEVEL="STRUCTURE" COMMAND="EXPLICIT" ACTIVE.DOC="306D0754" ACTIVE.LOC="AR:1;PT:4" MOD.LEVEL="1" PASSIVE.LOC="AR:5"?>
<ARTICLE IDENTIFIER="005">
<TI.ART>Article 5</TI.ART>
<STI.ART>Recovery of costs</STI.ART>
<?CLG.MDFO ID="O002001M003000" IDREF="C002001M003000" ACTION="REPLACED" LEVEL="STRUCTURE" COMMAND="EXPLICIT" ACTIVE.DOC="308D0162" ACTIVE.LOC="AR:1;PT:3" MOD.LEVEL="1" PASSIVE.LOC="AR:5;PA:1"?>
<PARAG123 IDENTIFIER="005.001">
<NO.PARAG>1.</NO.PARAG>
<ALINEA>All costs resulting from issuing the accompanying documents pursuant to Article 2(2) shall be borne by the food business operator responsible for the consignment or its representative.</ALINEA>
</PARAG123>
<?CLG.MDFC ID="C002001M003000" IDREF="O002001M003000"?>
<PARAG IDENTIFIER="005.002">
<NO.PARAG>2.</NO.PARAG>
<ALINEA>All costs related to official measures taken by the competent authorities as regards non-compliant consignments shall be borne by the food business operator responsible for the consignment or its representative.</ALINEA>
</PARAG>
</ARTICLE>
<?no_smark?>
<?CLG.MDFC ID="C001001M004000" IDREF="O001001M004000"?>