I'm not a big fan of the unary plus solution

I agree, I was just keeping the examples in line with what the map docs were saying. Personally in this case I'd prefer map { (...) } ..., since it makes it look obvious that returning a list is intentional. OTOH I also use map {$_=>1} ... very often, but that one doesn't cause any parse trouble.

The map +{...}, ... stuff is also mentioned in the map docs, although I haven't yet seen it used in the wild - personally I'd probably write map { {...} } .... As you can tell I usually prefer map BLOCK LIST over map EXPR, LIST.

... to force an anon hash constructor use +{:

my @hashes = map +{ lc($_) => 1 }, @array # EXPR, so needs
                                          # comma at end
[download]

to get a list of anonymous hashes each with only one entry apiece.