gistfile1.rb

# In this scenario, we initialize the variable,
# which is parsed *after* we access it, because
# the interpreter is always left-to-right.
[] << walrus if (walrus = :bubbles)

# Note: the value *does* change before the append
# happens.
walrus = nil
[] << walrus if (walrus = :bubbles)

# To better illustrate this, let's use our
# friend, nil.  No NameError here.
[] << nil if (walrus = :bubbles)

# Could also do something like this in your sample
[] << walrus || :bubbles