Using the CURL module in previous versions of PHP you could upload a file in a HTTP multipart formpost in a script like this:

     $ch = curl_init($APP);  
     curl_setopt($ch, CURLOPT_POSTFIELDS, array
('sampfile'=>"@$sampfile"));
     $postResult = curl_exec($ch);
     curl_close($ch);

With 4.1.0 (and what's currently in CVS), the CURL module has been modified to use the more proper libcurl function to deal with formposts, but it has the side-effect that pre-pending a file name with @ no longer works.

This is something that needs to be checked for and addressed in the ext/curl/curl.c source code if the above functionality is still wanted.

The functionality with a @-prepended file name is not documented anywhere in the PHP curl documentation AFAIK, but there are users out there that have found about this feature (it is a standard curl way of doing it using the command line) so there might be a point to continue supporting this.

(I am the libcurl maintainer, this report is based solely on source code auditing, I have not ran any PHP code to find out.)