use Win32::API::Prototype;

ApiLink( 'Kernel32', q[ HANDLE GetProcessHeap(void) ] ) or die $^E;
ApiLink( 'kernel32', q[ DWORD HeapCompact( HANDLE hHeap, DWORD dwFlags ) ] ) or die $^E;

my @idsMap;
my @AoH;
my $cnt = 1;

$|++;

for my $i ( 1 .. 40 ) {
    my $start = "aaa";
    my %hash; keys %hash = 250_000;
    printf "\r$i\t";
    for my $j ( 1 .. 250000 ) {
        $hash{ "$cnt $i $j $start" } = $cnt;

        $cnt++;
        $start++;
    }
    $AoH[$i] = \%hash;
}

print "Total size: ", total_size( \@AoH );

undef @AoH;

print "did undef of array\n";

<>;

print HeapCompact( GetProcessHeap( 0 ), 0 ) or die $^E;

...