More than 500 results are supported so long as you do not generate a live query

yt/subscribe.pl

@@ -20,7 +20,7 @@ my $EXTRAS_FILE = 'extra_videos.ini';
 my $CURL_BIN    = 'curl';
 my @CURL_ARGS   = ('-4', '--insecure', '-C', '-');
 my $BATCH_SIZE  = 50;
-my $MAX_INDEX   = 500;
+my $MAX_INDEX   = 2500;
 my $API_URL     = 'https://gdata.youtube.com/feeds/api/';
 my %API         = (
 	'search' => {