use subs qw(system); 
my $SYSTEM_SUCCESS = 0; 
sub system { 
    print "***\n"; 
    print "system @_\n"; 
    print "***\n\n"; 
    return $SYSTEM_SUCCESS; 
} 
local @ARGV = @test_args; 
do 'launch_rockets.pl'; 

##</code><code>##

use Proc::Background; 

##</code><code>##

Proc::Background->new('perl', 'launch_missiles.pl');