if ($pid=fork() ) {
    select(undef,undef,undef,.1);
        open (STDOUT, ">test.txt");
    print "parent\n";
    
} else {
    print "child\n";
}

##</code><code>##

if ($pid=fork() ) {
    #select(undef,undef,undef,.1);
    print "parent\n";
} else {
    open (STDOUT, ">test.txt");
    system("echo child");
}