use POSIX qw(sys_wait_h);
use strict;

...

if ($cdrpid = open(CDREC, "|-")) {
    if ($isopid = open(MKISO, "-|")) {
        my ($rin, $nfd) = ("","");
        vec($rin, fileno(CDREC), 1) = 1;
        if (not($nfd = select($rin, $rin, undef, 20))) {
            die "argh timeout";
        }
        while (<MKISO>) {
            print CDREC;
        }
        close(MKISO);
    } else {
        exec "$OPT{isobin}", '-r', @ARGV;
    }
    close(CDREC);
} else {
    exec "$OPT{cdbin}", "speed=$OPT{speed}", dev=$OPT{dev}", "tsize=@tsize", '-waiti', '-data', '-';
}

waitpid($isopid, &WNOHANG);
waitpid($cdrpid, &WNOHANG);