That link kind of confirms what I was thinking. Having said that, I can't see any direct way of removing things from the header. I tried completely cleaning out the header by doing this:.

  my @myheaders; 
  my $curl = WWW::Curl::Easy->new;
  $curl->setopt(CURLOPT_HTTPHEADER,\@myheaders);
  # That should have wiped out the default header assumptions that inc
+lude
  # Expect: 100-continue --which we don't want

  ### Do the rest of the header stuff via setopt:
  $curl->setopt(CURLOPT_URL,${uri});
[download]

Despite this, it seems to insist on the keepalive stuff