# /tmp/child-child.pl
print "I'm exec'd: $$\n";

##</code><code>##

#!/usr/bin/perl

use strict;
use warnings;

print "I'm parent ($0): $$\n";
my $child = fork;
defined $child or die "Can't fork: $!\n";

unless ($child) {
    print "I'm child ($0): $$\n";
    exec $^X, '/tmp/child-child.pl';
}

##</code><code>##

$ perl /tmp/main.pl
I'm parent (/tmp/main.pl): 12499
I'm child (/tmp/main.pl): 12500
I'm exec'd (/tmp/child-child.pl): 12500