$number = oct('0644');
  $number = eval('0644');  # same

##</code><code>##

my $n = ($x<<24) + ($y<<16) + ($z<<8) + 0x40;
$rect->set('fill-color-rgba' => $n);

##</code><code>##

my $n = ($x<<030) + ($y<<020) + ($z<<010) + 0x40;
$rect->set('fill-color-rgba' => $n);

##</code><code>##

my $n = ($x * 2**24) + ($y * 2**16) + ($z * 2**8) + 0x40;
$rect->set('fill-color-rgba' => $n);