ruby weirdness

weird_ruby.rb

class TestApp
  def run
    puts "foo is correctly 'foo': #{foo.inspect}"
    unless foo
      puts 'foo is nil' # This line is never hit, but the next line appears to get executed.
      foo = nil # Remove this line and it works as expected.
    end
    puts "foo is incorrectly nil: #{foo.inspect}"
  end

  def foo
    'foo'
  end
end

TestApp.new.run