3rd arrayref

That's there for historical reasons :-)   Actually, this is true, it was there in my first (pre-post) take and it basically got left in. One less dereference is good. Thanks.

map vs. foreach

For many years I only ever used foreach but that was because it wasn't available until Perl5. I then didn't use it for much the same reasons you give. About 2-3 years ago I was doing some benchmarking and was amazed at how much faster map was (especially the map BLOCK LIST form) - grep had a similar speed efficiency. I still use foreach; however, usage has made the map format easier on the eyes and I use it on a daily basis without really given it a second thought.

\my LIST

I was aware of this. It fails in extraordinarily interesting ways on various 5.6 versions. I now avoid it like the plague!

So that leaves us (or at least me) with:

my (@evens, @odds);
my @all = (\@evens, \@odds);
map { push @{$all[$_ % 2]}, $_ } split /,/, $scalar;
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Regards,