Hm. Seems to me that a list in a scalar context does return the last item:

print scalar (1,2,3);;
Useless use of a constant in void context at (eval 18) line 1, <STDIN>
+ line 16.
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And map and grep each return lists ...

...except, when they find their return context is SCALAR they chose not to return a list, but instead they return a scalar, which happens to be the size of the list they would have returned had they found themselves in a list context.

...except also when they find themselves in a void context, in which case they chose not to return anything at all.

It mostly a matter of words, but I think it is wrong to say "map and grep each return lists", when like any other perl function they can chose whether to return a list, a scalar or nothing at all depending upon the context in which they are called.