in reply to anyevent http 404code

The relevant info in the AnyEvent::HTTP documentation refers to request headers and reads
   You really should provide your own "User-Agent:" header value that is appropriate for your program - I wouldn't be surprised if the default AnyEvent  string gets blocked by webservers sooner or later.

The server blocks the AnyEvent request, but works ok if you indicate another valid User-Agent. Like
http_get $url, headers => { 'User-Agent' => 'curl/7.47.1' }, sub { [...]