The trick is to find out what the rule is.

And what would the "rule" in your example be? And why?

I really haven't the slightest idea what this is, and what it is supposed to do, but it looks interesting

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W5kIHBhY2soKS4gQnV0IGRvIHlvdS
ByZWNvZ25pc2UgQmFzZTY0IHdoZW4
geW91IHNlZSBpdD8gIC0tIEp1ZXJk