From http://cpansearch.perl.org/src/SHAY/libnet-3.10/lib/Net/FTP.pm

my $localfd = ref($local) || ref(\$local) eq "GLOB";

  if (!defined($remote) and 'STOU' ne uc($cmd)) {
    croak 'Must specify remote filename with stream input'
      if $localfd;
...
[download]

While there are times $temp may seem to be a filename, it is actually an object. Im **guessing** that $ftp->put("$temp") || die $ftp->message; will fix that