my @files = ("C:/foo.jpg", "C:/bar.jpg");
my $ua  = LWP::UserAgent->new();
my $req = POST $url, Content_Type => 'form-data',
    Content => [
        submit => 1,
        (map { "file".($_+1) => [ $files[$_] ] } 0..$#files),
    ];
[download]