use POSIX qw(open close);

my $open_dev_null = shift;

for (my $i = 3; $i <= 31; ++$i) {
    close($i);
}
use vars qw(@fds);
if ($open_dev_null) {
    @fds = map {open('/dev/null', O_RDONLY, 0)} (3..31);
}
print $$, "\n";
chdir('/');