sub check {
  my ($url) = shift;
  $url =~ m{http://([^\:|/]*)}s;
  my $host = $1;
  my $req = HTTP::Request->new(HEAD => $url);
  $req->header('Host' => $host);
  $req->header('If-Modified-Since' => time2str($mtime));
  my $resp;
  $resp = $ua->request($req) or warn "Response fuer $url fehlgeschlagen: ",$resp->status_line,"\n";
  print $resp->is_success;

  if(! $resp->is_success and $resp->code == RC_NOT_MODIFIED) {
    print "$url wurde seit ",time2str($mtime)," nicht geaendert.\n";
  } elsif (! $resp->is_success) {
    print $url, " => ", $resp->status_line, "\n";
  } elsif($resp->previous and $resp->previous->is_redirect) {
    check($resp->request->url);
  } else { 
    print "$url wurde geaendert!\n"; 
  }  
}