Mandelbrot in Perl 6

I decided to take a stab at translating mandel.pl from The Computer Language Benchmarks Game to Perl 6. I got rid of the threading, and because I was unable to get pack working (not there or just 5 AM programming issues?), I switched it from a P4 binary file to a P1 ASCII file. The resulting code runs in 3 minutes and 20 seconds, where the unthreaded version of the original runs in 0.2 seconds, so there is a lot of room for improvement here.

	# The Computer Language Benchmarks Game
	# http://shootout.alioth.debian.org/
	# implemented by Greg Buchholz
	# streamlined by Kalev Soikonen
	# parallelised by Philip Boulain
	# modified by Jerry D. Hedden
	# translated to Perl 6 by SF
	use v6;
	constant ITER = 50;
	constant LIMITSQR = 2.0 ** 2;
	my ($w, $h);
	$w = $h = shift @*ARGS || 80;
	# Generate pixel data for a single dot
	sub dot($x, $y)
	{
	my ($Zr, $Zi, $Tr, $Ti) = (0.0,0.0,0.0,0.0);
	my $i = ITER;
	my $Cr = 2 * $x / $w - 1.5;
	my $Ci = 2 * $y / $h - 1.0;
	while $Tr + $Ti < LIMITSQR && $i--
	{
	$Zi = 2.0 * $Zr * $Zi + $Ci;
	$Zr = $Tr - $Ti + $Cr;
	$Ti = $Zi * $Zi;
	$Tr = $Zr * $Zr;
	}
	return $i == -1;
	}
	# Generate pixel data for range of lines, inclusive
	sub lines(Num $low_y, Num $high_y)
	{
	for $low_y..$high_y -> $y
	{
	say join ' ', map { dot($_, $y) }, 0..$w-1;
	}
	}
	print "P1\n$w $h\n";
	lines(0, $h);

view raw mandel.pl hosted with ❤ by GitHub

I'll probably also take a stab at revamping the dot function to use the Complex type, assuming it actually is implemented, and maybe making lines feel more Perl 6ish.