I have always been under the impression that map assigns to a list, like foreach does, but this doesn't seem to be true. In truth, judging from my experiences as well as the form of a map call, map returns a list that the array or hash you have created is _then_ set to.

That's exactly what's happening. First the map is fully evaluated. It returns a list, and then that list is stored into the array. Similarly, you could use map without storing it (say, in void context, or passing the result to a function like print, or...) and it would evaluate it fully, and then do whatever it's supposed to with it. Put another way, if you were to write

$a = $a + 1;
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would you be surpised that it doesn't blow up ("But $a can never be one more than itself!")? No, it first evaluates the new value, and then does the assignment.