the bullet proof way:

my $pid = fork;
if (defined $pid and $pid == 0) {
  open STDOUT, ">", $fn or die;
  exec $script, @args;
  exit 1;
}
if ($pid) {
  waitpid($pid);
  $? and die "error on child: $?"
}
else {
  die "unable to fork: $!";
}
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