#!/usr/bin/perl -wl
use strict;

defined (my $pid = fork) or die "Cannot fork: $!";
unless ($pid) {
    for (1 .. 20) {
        print "CHILD: $_";
        sleep 1;
    }
    exit 0;
}

for (1 .. 20) {
    print "PARENT: $_";
    sleep 1;
}