Also, it depends on which language you're using...

    $ irb
    irb(main):001:0> a = 1
    => 1
    irb(main):002:0> b = 2
    => 2
    irb(main):003:0> b, a = a, b
    => [1, 2]
    irb(main):004:0> puts "#{a} #{b}"
    2 1
    => nil

(obviously this has the same flaw you mention, the interpreter is doing stuff for you. It follows the letter of the 'no intermediate variables' only.)