if (can_send($file)) { # we assume you can program whatever rules you need here
  open(INP,"<$file") || die "Can not open $file:$!\n"; # but  handle that in can_send
  my MIME::Types $types = MIME::Types->new;
  my $mime = $types->mimeTypeOf($file) || 
      "application/octet-stream";
  print header("Content-type: $mime");
  binmode(INP);
  binmode(STDOUT);
  while (<INP>) {
    print $_;
  }
  close(INP);
}