Parallel list generators (race)

@results := map { .say; $_ * 2 }, @data;
# nothing output yet, map is lazy

@results := eager map { .say; $_ * 2 }, @data;
# eager evaluation forced
# each element of @data printed in sequence

@results = hyper map { .say; $_ * 2 }, @data;
# elements of @data printed in any order
# @results same order as @data