use warnings;
use strict;
use Tree::Simple;

# make a tree root
my $tree = Tree::Simple->new("0", Tree::Simple->ROOT);

while(<DATA>) {
chomp;
my ($child, $parent) = split /:/;
my $sub_tree = Tree::Simple->new("$parent", $tree);

# explicity add a child to it
$sub_tree->addChild(Tree::Simple->new("$child"));

}

$tree->traverse(sub {
    my ($_tree) = @_;
    print (("\t" x $_tree->getDepth()), $_tree->getNodeValue(), "\n");
});


__DATA__
apple:fruit
granny smith:apple
fuji:apple
orange:fruit
blood orange:orange
mandarine:orange
dwarf fuji:fuji


##</code><code>##


$ perl test.pl
fruit
        apple
apple
        granny smith
apple
        fuji
fruit
        orange
orange
        blood orange
orange
        mandarine
fuji
        dwarf fuji


##</code><code>##


1
        1.1
2
        2.1
        2.1a
        2.2
3