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Hehe. You’re going to love this! (Warning: some of you are going to hate this.) Watch me skip every other element in an array with a flip-flop.

 >> s = true
 >> (1..10).reject { true if (s = !s) .. (s) }
 => [1, 3, 5, 7, 9]

Well, actually, that’s not so neat, since such a thing can simply be done with a single assignment in the block.

 >> s = true
 >> (1..10).reject { s = !s }
 => [1, 3, 5, 7, 9]

BUT! BUT! Tell me, can you hop to every third element in an array using only booleans and assignment? My flip-flops can jump that much higher.

 >> s = true
 >> a = (1..10).reject { true if (s = !s) .. (s = !s) }
 => [1, 4, 7, 10]

Now, let’s see you beat this reassembling of our array into threes. My flip-flops bunch triplets together!

 >> s = true
 >> a = (1..10).inject([]) do |ary, v| 
 >>       ary << [] unless (s = !s) .. (s = !s); ary.last << v; ary
 >> end
 => [[1, 2, 3], [4, 5, 6], [7, 8, 9], [10]]

Well, maybe this one you can beat with a modulo, but mine will be more detestable for sure.