for my $machine ( @machines ) {
    open my $out, '>', "$machine.dat" or die $!;
    for my $cmd ( @commands ) {
        my $content = get "$machine/$cmd";
        print $out $content;
    }
    close $out;
}

##</code><code>##

for my $machine ( @machines ) {
    async {
        open my $out, '>', "$machine.dat" or die $!;
        for my $cmd ( @commands ) {
            my $content = get "$machine/$cmd";
            print $out $content;
        }
        close $out;
    }->detach;
}

##</code><code>##

my $running :shared = 0;             ## This tracks the number of concurrent threads
for my $machine ( @machines ) {
    async {
        { lock $running; ++$running; }          ## incr on start
        open my $out, '>', "$machine.dat" or die $!;
        for my $cmd ( @commands ) {
            my $content = get "$machine/$cmd";
            print $out $content;
        }
        close $out;
        { lock $running; --$running; }          ## decr on finish
    }->detach;
    sleep 1 until $running < 10;                ## sleep a bit if more than 10 are running
}

sleep 1 while $running;     ## Make sure the main threads waits for the last few threads to finish