Without seeing your code, it will be very hard to suggest things on how to make it do what you want.

You have discarded all the obvious things that would make it easier, because you say that you really need this.

Ideally, you show us some minimal code that reproduces the problem so that we can run it ourselves. For example, the following could be a start:

#!perl
use strict;
use warnings;

my $memory_eaten = 8 * 1024 * 1024 * 1024; # 8GB, adjust to fit

my %memory_eater = (
    foo => scalar( " " x $memory_eaten ),
);

my $cmd = "foo bar";
system($cmd) == 0
    or die "Couldn't launch '$cmd': $!/$?";

[download]

Updated: Actually make the hash eat memory by creating a loong string

In reply to Re^4: System call doesn't work when there is a large amount of data in a hash by Corion
in thread System call doesn't work when there is a large amount of data in a hash by Nicolasd

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