You might play with this a bit:

#!/usr/bin/perl
use 5.14.0;
use warnings;
use autodie;
use Data::Dumper;

my $t = myTree::create_tree(5);
print Dumper($t);

package myTree;

sub create_tree {
    my $depth = shift;
    my $object = {
        left =>$depth ? create_tree($depth-1) : undef,
        right=>$depth ? create_tree($depth-1) : undef
    };
    return bless $object;
}
[download]

...roboticus

When your only tool is a hammer, all problems look like your thumb.