afaik, the memory that you'll free if a var is going out of scope is never released back to the OS, so perl keeps the memory allocated for future use within the script.

In other words, the memory is free to reuse by the same perl process, but not for other processes on your system.

I've tested this using these 3 simple scripts, and you can see doing a ps -o vsz,command | grep perl (or similar type of command, adapt to your OS, in my case it's FreeBSD), that in the first 2 cases the memory usage by the relevant perl processes is the same:

#!/usr/bin/perl
use strict;
# case 1: array uses a lot of memory, and goes out of scope
$0 = "highmemusage_going_out_of_scope";
{
 my @aap = map { $_ * $_ } ( 0 .. 100000 );
}
sleep 300;
[download]

#!/usr/bin/perl
use strict;
# case 2: array uses a lot of memory, and stays in scope
$0 = "highmemusage_staying_in_scope";
my @aap = map { $_ * $_ } ( 0 .. 100000 );
sleep 300;
[download]

#!/usr/bin/perl
use strict;
# case 3: use as baseline mem usage of your perl
$0 = "reference";
sleep 300;
[download]

Anybody more familiar with perl memory allocation please correct me if I'm wrong,