use LWP;

my $ua = LWP::UserAgent->new;
my $req = HTTP::Request->new( POST => $url);

$req->content_type('image/jpeg');
open(FILE,$filename);
$req->content(join('',<FILE>));
close(FILE);

my $res = $ua->request($req);

die("Bzzzzzzz, error!") unless $res->is_success;
[download]

If server does not support direct upload of picture this way, you should probably encode it as a part of HTML form. Use content type of 'multipart/form-data' and you should probably use some (MIME?) modules to build up a content with proper headers.