Thanks for all your help. I got the boundary value to appear after much finagling with the Content portion.
Authentication was driving me nuts, until, I came across a wonderful little post from tilly. This place is full of Fonzies!!

Re (tilly) 2: HTTP::Headers, HTTP::Request, Authentication, LWP::Useragent

The working code looks like this:

 my $ua  = LWP::UserAgent->new;
 my $uri = "http://" . "$uid" . ":" . "$pass" . "@" . "myserver.com/LL
+S/GenPublishMessage";
 my $req = $ua->request(POST "$uri",
                        Content_Type => 'multipart/form-data',
                        Content => [ xmlmsg=>$xmlmsg ]);
[download]

Get Strong Together!!