also XPM format (used for icons in Tk) can be fed with an array like in my woodpeaker icon

I rewrote your exmple using GD and maybe is faster (untested).

my $W = 100;
my $W = 100;

use GD;
 
# create a new image
$im = new GD::Image($W,$W) or die "called to new GD::Image  has failed
+.";;

for my $x (0..$W){
  for my $y (0..$H){
    my $rgb = $result->[$x + $y * $W];
    next unless defined $rgb;
    # ARGB here, or any other scheme
    my $R = ($rgb & 0x00FF0000) >> 16;
    my $G = ($rgb & 0x0000FF00) >> 8;
    my $B = ($rgb & 0x000000FF);
    
    my $color = $im->colorAllocate($R, $G, $B);
    $im->setPixel($x, $y, $color);
    
  }
}

open my $outfile, '>', 'out.png' or die;
binmode $outfile;

print $outfile $im->png(0); # 0 is no compression. Possible values 0-9
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