my $parser = XML::Parser->new(ErrorContext => 2, Style => "Tree");
my $xso = XML::SimpleObject->new( $parser->parse($content) ) or die "could not parse!";
check_tag($xso);
...

##</code><code>##

#!/bin/perl -w
use strict;

use XML::Twig;

my $twig = XML::Twig->new();
$twig->parse( \*DATA)
            or die "could not parse!";
# the #ELT argument means that we will get only the
# "real" elements, as opposed to the ones containing the text
foreach my $tag($twig->descendants( '#ELT')) {
    print $tag->gi;
    print " ", $tag->text if( is_field( $tag));
    print "\n";
  }

sub is_field
  { my $tag= shift;
    return 1 if( ($tag->children == 1) && $tag->first_child->is_text);
    return 0;
  }

__DATA__
<doc id="id1">
  <elt id="id2">elt 1</elt>
  <elt id="id3">
    <subelt id="id4">subelt 1</subelt>
    <subelt id="id5">subelt 2</subelt>
    <subelt id="id6">subelt 3</subelt>
  </elt>
  <elt id="id7">elt 3</elt>
  <elt id="id8"><subelt id="id9">subelt 4</subelt></elt>
</doc>