How do you think ruby parses this expression?
   a = 1 + b = 2 + c = 4 + d = 8

Originally I thought that operator precedence would result in
   a = (1 + b) = (2 + c) = (4 + d) = 8
and since an assignment requires a variable, that would result in a SyntaxError. 
But instead it seems that everything on the right side of the assignment 
operator is evaluated first:
   a = (1 + (b = (2 + (c = (4 + (d = 8))))))

That had me really puzzled at first but I guess the behavior makes a certain 
sense, and it's more useful than a syntax error. Ruby's tolerant parser wins again!

Daniel