Wow, and here I thought the purpose of map was to evaluation the block or expression over the range of the list passed to it. Perhaps you thought that by "side-effect", I meant that the creation of the output list was an accidental, unintentional thing. No. I meant "side-effect" in the same sense that most people use it with regards to programming.
I'm quite well aware of the differences between map and foreach, and the conditions under which you would choose one or the other. Try to take a less confrontational tone, it will usually get you better responsiveness from others.