open DAT, "ads.dat" or die "Error: cannot open data file: $!\n";

@imgdata=<DAT>;
@imgs = grep { s/^[^|]+\|([^|]+)\|[^|]+\|(?:internal|partner)$/$1/ } @imgdata;

$img  = $imgs[int(rand($#imgs+1))];
print "Location: $img\n\n";