### INIT pragma
    use strict;
    use warnings;

### INIT vars
    my  $data_root          = {};
        $data_root->{car}   = {
            wheels  => 4,
            doors   => 4,
            color   => 'blue',
        };

        $data_root->{bike}   = {
            wheels  => 2,
            doors   => undef,
            color   => 'blue',
        };

### DISPLAY
    print $data_root->{car}{color};
    print "\n---------------------\n";

    print $data_root->{bike}{color};
    print "\n---------------------\n";

    print $data_root->{$_}{wheels},"wheels "foreach(keys %{$data_root});
    print "\n---------------------\n";