$pg->add_fact( owns => ('Ovid', 'Cheap Whiskey'));

##</code><code>##

[0]{2}[1]{3} = {}
[1]{3} = {}

##</code><code>##

# object ids are hashes and argument positions are arrays
$self->{_arg_levels}{2}[0]{2}[1]{3};

##</code><code>##

    $_ = $self->_get_vertex( $_ ) foreach @args;

    # @important is a list of argument positions that are 
    # not null (e.g, undef, empty string, or '_')
    my $a = shift @important;
    while( my $z = shift @important ) {
        return if !$self->_check_path($predicate_id,$a,$z,@args[$a,$z]);
        $a = $z;
    }
    return 1;

##</code><code>##

$pg->add_fact( gnarfle => qw/ foo bar baz / );
$pg->add_fact( gnarfle => qw/ foo tac toe / );
$pg->add_fact( gnarfle => qw/ tic tac toe / );

my $results = gnarfle( qw/ $one _ $two / );
# or
my $results = gnarfle( qw/ $one tac $two / );

##</code><code>##

foo baz
foo toe
tic toe

##</code><code>##

foo toe
tic toe