Options for pack 
Option                Usage
-after=>$widget       Places this widget after $widget.
-before=>$widget      Places this widget before $widget.
-expand=>1            Allows widget to expand to fill unused space.
-expand=>0            Turns off expansion in filling unused space.
-fill=>x              Fills widget out horizontally.
-fill=>y              Fills widget out vertically.
-fill=>both           Fills widget out both horizontally and vertically.
-side=>bottom         Packs widget from bottom.
-side=>left           Packs widget from left.
-side=>right          Packs widget from right.
-side=>top            Packs widget from top.