#!/usr/bin/env perl

use strict;
use warnings;

use IPC::Run qw(run);

my $str;

my $count = 0;
while (1)
{
  $count += 10;
  $str .= "1111111111";

  run [echo => $str], '|', [grep => 'foo'];
  print "$count " unless ($count % 10000)
}

##</code><code>##

 % ./t2.pl
10000 20000 30000 40000 50000 60000 70000 80000 90000 100000 110000 120000 130000 exec failed: Argument list too long at ./t2.pl line 16.
 at ./t2.pl line 16.

##</code><code>##

# wc -c fw2.save
165670 fw2.save