Raku By Example
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my $start = now;

# Promise to calculate in chunks
$start = now;
my @p = (1..4).map( -> $t {
    start {
        my $total = 0;
        for (250_000*($t-1)+1)..(250_000*$t) -> \num {
            $total += 1e0/num;
        }
        $total;
    }
});
say (await @p).sum;
say (now - $start);

# Race to calculate in chunks
$start = now;
say (1..1_000_000).race(:batch(250_000)).map(1e0/*).sum;
say (now - $start);

## await

my @promises = ^3 .map: {
    start {
        .say; sleep 1;
        $_ * 4;
    }
};

say "Started! {now - INIT now}";
say await @promises;
say "All done! {now - INIT now}";