You can only run this code from another form that provides the filename and handle, without them you get the error. I've added a simple form to your script to prove it works OK

#!perl -wT

use CGI qw(:standard); #### be sure to change this
use CGI::Carp qw ( fatalsToBrowser );
use strict;
use Fcntl qw ( :DEFAULT :flock );
use constant UPLOAD_DIR => "c:/upload/";

my $q    = new CGI;
my $filename = $q->param('file');
my $fh       = $q->upload('file');

if ($fh){ #### check for filehandle

  $filename        =~ s/[^\w.-]/_/g;
  if ($filename =~ /^(\w[\w.-]*)/) {
    $filename = $1;
  }
  else {
    error($q, "Invalid file name." );
  }
  my $upload_dir = UPLOAD_DIR . $filename;
  sysopen(OUTPUT, $upload_dir, O_CREAT | O_RDWR | O_EXCL);
  my $buffer = "";
  while (read($fh, $buffer, 16384)) {
    print OUTPUT $buffer;
  }
  close OUTPUT;

  print $q->header,
        $q->start_html("At long last"),
        $q->h1("done dude...doh"),
#### add button to reset form
        $q->start_form( -action => url () ),
        $q->submit ( -name=>"done", -value=>"Done"),
        $q->end_form();
####
        $q->end_html;

#### simple form to choose file to upload
} else {
  print $q->header,
        $q->start_html("Upload File"),
        $q->start_multipart_form( -action => url () ),
        "File : ",
        $q->filefield (-name=>"file", -size=>60),
        $q->submit ( -name=>"submit", -value=>"Submit"),
        $q->end_form();
        $q->end_html;
}
[download]

poj