$filename = "c:/test.pl";
use HTTP::Request::Common qw(POST);
use LWP::UserAgent;

my $ua = new LWP::UserAgent;  

my $req = POST ('http://www.environet.gov.on.ca/dwws-app/DWWSApp?cmd=UploadSubmPage.uploadSubm',
                Content_Type => 'form-data',
                Content      => [
                                works_id => '2353245', 
                                lab_id   => '456436', 
                                filename => [$filename]
                                ]
                );
           
print $req->as_string; # looks OK
             
my $res = $ua->request($req);

print $res->as_string;