use strict;

# returns list of CD/DVD mountpoints or empty list
sub scan_cddvd { 
    my @drives   = ();
    my $mtabfile = "/etc/mtab";

    open my $mtfh, "<", $mtabfile or die "cannot open $mtabfile - $!";
    while( <$mtfh> ){
      my ($dev, $mountpoint, $fstype, $options) = split /\s+/;
      next unless $fstype =~ /udf|iso\d+/ && $options =~ /ro\b/; 
      #ro: the /ro/-test above should skip CDRW too
      $mountpoint =~ s/\\(0\d+)/chr(oct($1))/eg;  # resolve oct chars
      push @drives, $mountpoint;
    }
    close $mtfh;

    return @drives;
}

print "o <", join(">\no <", scan_cddvd), ">\n";