$childPid = open SON, "-|";

sub sigtrap() {
    print "\n";
    print("------      Killing all childrens then exeting ...      ------\n");
    if(defined($childPid) && ! ($childPid == 0)){
        killfam 'KILL', ($childPid);
    }
    print "\n";
    print "Exiting ... \n";
    exit(1);
}

if ($childPid) {
    #parent
    system("while true; do echo aabbcc >> $temp_file; sleep 2; done");
}else {
    print "[$$]: Child...\n"; 
    system("tail -f $temp_file >> $file &");
    exit(0);
}