my $got_lock;
use Fcntl;   # to get constants for O_CREAT | O_EXCL | O_RDWR
for ( 0 .. 5 ) {
    if ( sysopen(my $fh, "$base_dir/.lock", O_CREAT | O_EXCL | O_RDWR, 0600) ) {
        $got_lock = 1;
        close $fh;
      last;
    }
    sleep 2;
}
diehtml("Lock error $!\n") unless $got_lock;

##</code><code>##

system ("lockfile -2 -r 5 $base_dir/.lock")  == 0
        or diehtml("Lock error: ", $? >> 8, "\n");
        # TODO stop stderr of system