use POSIX;
my ($tmpfh, $name);
do {
    $name = POSIX::tmpnam()
} until
    sysopen( $tmpfh, $name, O_RDWR|O_CREAT|O_EXCL)
    or                       # if error, then
        $! !~ m/File exists/ # try again if bad name
        &&  die $!;          # else die