In Ruby why won't `foo = true unless defined?(foo)` make the assignment?

Question

What\'s going on here? What is the subtle difference between the two forms of \"unless\"?

> irb(main):001:0> foo = true unless defined?(foo)
=> nil         


        

Answer 1

August, all look fine in 1.8.7:

$ irb
irb(main):001:0> unless defined?(fooo); fooo = true; end
=> true
irb(main):002:0> fooo
=> true
irb(main):003:0> `ruby --version`
=> "ruby 1.8.7 (2008-06-20 patchlevel 22) [i486-linux]\n"