use strict;
use warnings;

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

##</code><code>##

use strict;
use warnings;

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