This isn't overly useful, but i think its an interesting way to multiply two integers. For a given function

f(a, b);

the obvious way to multply integers is simply to add a to itself b-1 times. The algorithm below, however, adds a shifted i times to the left if b is odd (b & 0x01 == 1), where i is a number from 0 (beginning) to whatever. After every iteration, shift b to the right, lather, rinse, repeat until no more b. Keep in mind, for all i know, i could be the first person to use this, or this may be common knowledge already. I really don't know. thought i'd post it and see what you all thought.

sub multiply {
        ($a, $b) = @_;
        $i=0; $product=0;

        do {
                $product += ($a << $i) if ($b & 0x01);
                $i++;
        }  while ($b>>=1);

        return $product;
}
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