Thanks, nitrogen. Following your info led to a couple of other neat discoveries, and a bunch more useful material [1].

As a result here are some new ways I learned to get 5 from 2 + 2:

  require 'fiddle'
  a = 2
  b = 2
  Fiddle::Pointer.new(a.object_id << 1).to_value.ceil + b
  => 5

Note: This happens because calling `to_value` on the `Fiddle::Pointer` object returns a Float (2.0000000000000004) instead of Fixnum (which was a surprise to me).

And here's another using `Object#tap`:

  a = 2
  (a + a).tap{|x| a = x + 1}.send(:eval,'a')
  => 5

[1] These links were helpful for me. The last one is an MIT licensed book called, "Kestrels, Quirky Birds, and Hopeless Egocentricity."

http://stackoverflow.com/questions/1872110/is-ruby-pass-by-r...

http://patshaughnessy.net/2014/1/9/how-big-is-a-bignum

http://stackoverflow.com/questions/2818602/in-ruby-why-does-...

http://combinators.info/#kestrels

Edit: line formatting