# assuming you've already populated @urls
# and done:
use LWP::UserAgent;
use strict;
use warnings;

# try this:
my @old_urls = @urls;
@urls = ();
my $user_agent = LWP::UserAgent->new;
while (@old_urls) {
  my $url = shift (@old_urls);
  my $response = $user_agent->get($url);
  if ($response->is_success) {
     push @urls, $url;
     # or, if you want to get more detailed:
     # push @urls, {
     #              url => $url,
     #              type => $response->content_type,
     #             };
   }
}