open(SENDMAIL, '|/usr/sbin/sendmail -oi -t')
   or (unlink ($outfile),
    diehtml("Can't fork for sendmail: $!\n"));

##</code><code>##

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;