while(<$formdata{upload}>) {
  print;
}

##</code><code>##

my $buffer;
while(read $formdata{upload},$buffer,1024) {
     print $buffer;
}

##</code><code>##

my $buffer;
my $max_size = 10 * 1024; # 10 KB but it can be whatever
my $size;
while(read $formdata{upload},$buffer,1024) {
     $size += 1024;
     if($size > $max_size) {
          print "Image is too big!";
          last;
     }
}