my @visited_urls = ($url_name);
  ...
  while (@website_links) { 
    if ((grep {$_ eq $website_links[0] } @visited_urls) > 0) 
##</code><code>##

  my %visited_urls = ($url_name => 1);
  ...
  while (@website_links) { 
    if ( $visited_urls{$website_links[0]} )