Turn off box axis 

@@ -25,6 +25,7 @@
     x_label_position   => 0.5,
     transparent        => 0,
     bgclr              => 'white',
+    box_axis           => 0,
     dclrs              => ['#ff782a', '#6daa3a', '#4d7296'],
 ) or die $graph->error;