If i do this

use Scalar::Util qw(weaken);
my $count = 3000;
do {
    print "".(`ps -p $$ -o size=`+0)." "
      if ! ($count % 100);
    my $x =  \("abcdefghijklmnopqrstuvwxyz" x 8000); 
    my $y = $x; 
    weaken $y;
} while $count--;
[download]

I get

1128 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544

But if I do this

use Scalar::Util qw(weaken);
my $count = 3000;
do {
    print "".(`ps -p $$ -o size=`+0)." "
      if ! ($count % 100);
    my $x = {x=>"abcdefghijklmnopqrstuvwxyz" x 8000};
    my $y = $x; 
    weaken $y;
} while $count--;
[download]

i get this

1128 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1544 1676 1676 1676 1676 1676 1676 1676 1676 1676 1676 1808 1808 1808 1808 1808 1808

The more iterations, the more it leaks. Why? (perl 5.10.0 here)