$ cat /tmp/p1
#!/usr/bin/perl

$| = 1;
for (1..10) {
    if (fork == 0) {
        print "$_\n" for 1..100;
        exit;
    }
}

$ perl588 /tmp/p1 > /tmp/x ; wc -l /tmp/x
900 /tmp/x
$ perl588 /tmp/p1 > /tmp/x ; wc -l /tmp/x
983 /tmp/x
$ perl588 /tmp/p1 > /tmp/x ; wc -l /tmp/x
1000 /tmp/x