$req=POST 'https://www.abc.com/fileUpload.aspx', Content_Type=>'multipart/form_data', Content => [__VIEWSTATE=>'dDwtMjRrKEnBI=',
aa=>'I',
file1=>['ABCD.DAT']]

$req->as_string;


##</code><code>##

POST https://www.abcd.com/fileUpload.aspx
Content-Length: 411
Content-Type: multipart/form_data

VIEWSTATE=dDwtMjRrKEnBI%3D&aa=I&file1=ABCD.DAT