use strict;
use warnings;
use Tree::DAG_Node;

my $root = Tree::DAG_Node->new ();
my $level = 0;
my $currMother = $root;

while (<DATA>) {
    chomp;
    s/^\s+//;
    my ($lineLevel, $tag, $tail) = split ' ', $_, 3;
    my $newDaughter;
    
    while ($lineLevel < $level) {
        $currMother = $currMother->mother ();
        --$level;
    }
    
    if ($lineLevel > $level) {
        $newDaughter = $currMother = $currMother->new_daughter ();
        die "Adjacent lines differ by more than one level at line $."
            if ++$level != $lineLevel;
    }
    
    $newDaughter = $currMother->new_daughter () unless $newDaughter;
    $newDaughter->name ($tag);
    $newDaughter->attribute ()->{data} = $tail;
}

print "<root>\n";
$root->walk_down ({callback => \&enterNode, callbackback => \&exitNode, _depth => 0});
print "</root>\n";


sub enterNode {
    my ($node, $options) = @_;
    
    return 1 if ! defined $node->{name};

    print ' ' x ($options->{_depth} * 3);
    print "<$node->{name}>";
    print $node->attribute ()->{data} if defined $node->attribute ()->{data};
    print "\n";
    return 1;
}


sub exitNode {
    my ($node, $options) = @_;

    return if ! defined $node->name ();

    print ' ' x ($options->{_depth} * 3);
    print "</$node->{name}>\n";
}


__DATA__
 0 HEAD 
 1 SOUR Reunion
 2 VERS V8.0
 2 CORP Leister Productions
 1 DEST Reunion
 1 DATE 11 FEB 2006
 1 FILE test
 1 GEDC 
 2 VERS 5.5
 1 CHAR MACINTOSH
 0 @I1@ INDI
 1 NAME Bob /Cox/
 1 SEX M
 1 FAMS @F1@
 1 CHAN 
 2 DATE 11 FEB 2006
 0 @I2@ INDI
 1 NAME Joann /Para/
 1 SEX F
 1 FAMS @F1@
 1 CHAN 
 2 DATE 11 FEB 2006
 0 @I3@ INDI
 1 NAME Bobby Jo /Cox/
 1 SEX M
 1 FAMC @F1@
 1 CHAN 
 2 DATE 11 FEB 2006
 0 @F1@ FAM
 1 HUSB @I1@
 1 WIFE @I2@
 1 MARR 
 1 CHIL @I3@
 0 TRLR