my $filename = "file.gif";
my $filepath = "/path/to/";
if(-e "$filepath$filename") {
  my $_binCheck = is_file_binary("$filepath$filename");
  if($_binCheck && $_binCheck == 1) {
    # print header for download and then open the file in binary mode and print to window for the attachment
  } else {
    # print header for download and open the file normally and print to window for the attachment
  }
} else {
   die "File does not exist: $filepath$filename";
}