I am still running into trouble with the data. I have changed the code to read like follows

my (@h,@c);
push @h, $_->{'hour'} foreach(@{$data});
push @c, $_->{'count'} foreach(@{$data});
my $new = [ \@h, \@c];
print (\@new);


#@data=(["1st","2nd","3rd"],
#        [9,4,7]);


#  I have a hash table with $data[$index]{'hour'} and $data[$index]{'c
+ount'}
#
$graph= GD::Graph::lines->new(400,300);
$graph->set(
    x_label => 'Hour',
    y_label => 'Transaction Volume',
    title => 'Number of transactions per hour',
    y_max_value => 20,
    y_label_skip => 1,
    y_tick_number => 1);

    #$gd = $graph->plot(\@data);

    open (IMG,'>file.png') or die $!;
    binmode IMG;
    print IMG $graph->plot(\@new)->png;

    close IMG;
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but when I run it I still receive the same error. If I uncomment the @data lines and plot to @data instead of @new it works. Any ideas?