use GD;

# Create a new transparent image
my $image = GD::Image->newTrueColor(1, 1);
$image->alphaBlending(0);
$image->saveAlpha(1);
my $transparent = $image->colorAllocateAlpha(0, 0, 0, 127);
$image->transparent($transparent);

# Output the image
print "Content-Type: image/png\n\n";
print $image->png;