Regarding #2: The fact that map output size differs from input size doesn't mean there's no benefit to nesting vs. chaining. The benefit I expected was in memory overhead (from not having so many copies resident at once) more than in reduction of operations (from copying multiple times). I agree with your point about nesting being harder to read; that's why I suggested it as an optimization.

Putting the idea in better terms, I'm suggesting that map, in an ideal world where perl development was effortless, should behave like (1..100000): when its output is assigned, the range generates the whole list; but when its output is used iteratively (at least, in a foreach loop), it simply generates one output value at a time, as needed. map, grep, and ranges could all behave that way when feeding map, grep, or foreach.