Thanks! I used Albannach's suggestion, though it seems I need to prepend the directory name explicitly. Anyway, the code below works... thanks gang!
nop

use strict;

my $dir = shift;
if (!$dir) {die "perl $0 [startdir]\n";}

my %size;
&dir_tree_size($dir);

foreach my $dir (
         map { $_->[1] }
         sort { $b->[0] <=> $a->[0] }
         map { [$size{$_}, $_ ] } keys %size) {
    print "$size{$dir}\t$dir\n";
}

sub dir_tree_size {
  my $dir = shift;
  warn "$dir\n";
  my ($i,$total);
  $total = 0;
  opendir DIR, $dir;
  my @files = grep !/^\.\.?$/, readdir DIR;
  for $i (@files) {
    if(-d $dir . "\\" . $i) { 
    $total += &dir_tree_size($dir . "\\$i") }
    else { $total += -s $dir . "\\" . $i}
  }
  $size{$dir} = sprintf("%8d K", $total / 1024);
  return $total;
}
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