my %results :shared;
my $done    :shared;
async {
    my %comps;
    for my $i ( 1 .. 1e6 ) {
        $comps{ $i } = $i ** $i;
    }
    %results = %comps;
    $done++;  # using $done = 1 doesn't want to work - more thought required!
}->detach;

my $c;
while( sleep 1 ) {
    print "timer event";
    last if $done;
}

pp scalar keys %results;