I understand that every method can have a block passed to it that is 
accessed using "yield".  I have a few more questions about this thought.

1) Is it possible to make the block optional?  If so, how does one 
determine that no block is present? Or, is it done by providing a 
default block?  If so, how?

2) Is it possible to pass multiple blocks to a method?  If so, how does 
one distinguish between them when yielding?

Thanks
David Corbin