You'll kick yourself.

The value of $shape for setting a square is 'square  ', not 'square'.

Update:

Of course, the spaces in your list of names serve no purpose. You cannot (in general) use spaces to align text, because not all fonts are fixed-width. And since you're telling pack to anchor => 'w', you'll get the desired(?) left-justification anyway.

Just say "foreach ('square','circle','polygon')" and have done with it...