my $response = LWP::UserAgent::
  -> new
  -> head("http://writeups.info/new-age/na09/Relaxing%20Songs%20Music%20-%20Wind%20Beneath%20My%20Wings.mp3");
if ($response->is_success and $response->content_type =~ m{^(?:audio|application)/(?:x-)?(?:mp3|mpeg)$})
{
    say "It's probably an MP3!";
}