"A few more details on that?"

My pleasure:

use Thread::Queue;
use strict;
use warnings;
use feature qw(say);

my $width  = 10;
my $height = 10;
my $queue = Thread::Queue->new();

for my $y ( 0 .. $width - 1 ) {
    my @colors;
    for my $x ( 0 .. $height - 1 ) {
        push @colors, mandelbrot();
    }
    $queue->enqueue( [ $y, @colors ] );
}

$queue->end;

while ( my ( $y, @colors ) = @{ $queue->dequeue } ) {
    say qq($_, $y, $colors[$_])for  0 .. $#colors;
}

# this is still a fake!
sub mandelbrot {
    int rand 20;
}

__END__

\monks>undef.pl
0, 0, 8
1, 0, 4
2, 0, 7
...
7, 9, 10
8, 9, 3
9, 9, 0
Can't use an undefined value as an ARRAY reference at C:\Dokumente und
+ Einstellungen\karl\Desktop\monks\undef.pl line 20.
[download]

This doesn't complain:

while ( my $item = $queue->dequeue ) {
    my ( $y, @colors ) = @$item;
    say qq($_, $y, $colors[$_]) for 0 .. $#colors;
}
[download]

Best regards, Karl