Helpful, indeed.
What I recognized:
- allocating a big chunk of memory at once is evil (for releasing it afterwards): 
use strict;
$| = 1;
print "$$\n";   #top -p $$
    
print "Test, Allocating a large string \n"; <>;
{
    my $foo = 'X' x 100000000; 
    print "Large String allocated.\n";<>;
    
    undef $foo;
    print "Large String deallocated.\n";<>;
}

print "2nd Large String.\n";<>;
{
#evil:    my $foo2 = 'X' x 100000000;
    my $foo2;   
    $foo2 .= 'x' x 1000 for (1 .. 100000);
    print "2nd Large String allocated.\n";<>;
    undef $foo2;
    print "2nd Large String deallocated.\n";<>;
}   
print "Now what? Press enter to exit";
<>;

[download]
As you can see the memory used for $foo2 is returned to the OS. So my initial example was not correct.

May I ask you another question, which puzzles me:
The above example also shows that at the end of the of script there are still 97m allocated (due to $foo). Also, the variable $foo2 does not use the previous allocated chunks of $foo (because the usage also rises up to total usage 192m.
Is the caused by the overhead of the internal memory handling of perl?
Thanks,

In reply to Re^2: Perl Garbage Collection, again by pkirsch
in thread Perl Garbage Collection, again by pkirsch

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