Perl 5 uses documentation to explain the implementation so saying "it is documented to return the number of elements in scalar context so it can't just as easily return the day of year instead" doesn't hold much water. Fortunately, Perl 6 is intended to have a complete specification allowing for any number of implementations. This has nothing to do with the issue I wanted to make though.

Your wording to me implies that map doesn't actually create the elements it counts. The docs say "In scalar context, returns the total number of elements so generated." which implies to me they are created. I know that there could be an optimization not to actually build up the return list such as happens when map is called in a void context with recent versions. If indeed it is as you say, a doc patch should be submitted to clarify.