use strict;
use warnings;

use LWP::UserAgent;
use LWP::Debug qw(+);

my $ua = LWP::UserAgent->new();

my $response = $ua->post(

    "http://toxicice.com/login.php", [

        username => 'xxxxxxx',
        password => 'xxxx',
        autlogin => 'off',
        redirect => '',
        login    => 'Log in',
    ]
);
$response->is_success or
    die "Login failed: ", $response->status_line, "\n";

With an invalid username/password (as above), it gives:

LWP::UserAgent::new: ()
LWP::UserAgent::request: ()
LWP::UserAgent::send_request: POST http://toxici
LWP::UserAgent::_need_proxy: Not proxied
LWP::Protocol::http::request: ()
LWP::Protocol::collect: read 398 bytes

... snipped ...

LWP::Protocol::collect: read 188 bytes
LWP::UserAgent::request: Simple response: OK

However, with a valid one it gives:

LWP::UserAgent::new: ()
LWP::UserAgent::request: ()
LWP::UserAgent::send_request: POST http://toxicice.com/login.php
LWP::UserAgent::_need_proxy: Not proxied
LWP::Protocol::http::request: ()
LWP::UserAgent::request: Simple response: Found
Login failed: 302 Found

$response->content is empty ('').

I updated some time ago to a more recent version of ActiveState Perl,
and probably LWP was upgraded as well. OTOH it might be a server thing.

perl -v
...
This is perl, v5.8.7 built for MSWin32-x86-multi-thread
...

query *
...
libwww-perl          [5.803.0.1] Web API for Perl
...

(Complete script is at:
http://johnbokma.com/perl/phpbb-remote-backup.html )

( If you want to test but have no PHP board, mail: phpbb at johnbokma
dot com, and I arrange a test log in, don't create a test login
yourself, thanks )

Add this:-

push @{ $ua->requests_redirectable }, 'POST';

sub redirect_ok
{
     # draft-ietf-http-v10-spec-02.ps from www.ics.uci.edu, specify:
     #
     # If the 30[12] status code is received in response to a request using
     # the POST method, the user agent must not automatically redirect the
     # request unless it can be confirmed by the user, since this might
change
     # the conditions under which the request was issued.

     my($self, $request) = @_;
     return 0 if $request->method eq "POST";
     1;

$VAR1 = bless( {
                  'max_redirect' => 7,
                  'protocols_forbidden' => undef,
                  'no_proxy' => [],
                  'protocols_allowed' => undef,
                  'use_eval' => 1,
                  'requests_redirectable' => [
                                               'GET',
                                               'HEAD'
                                             ],
                  'from' => undef,
                  'timeout' => 180,
                  'agent' => 'libwww-perl/5.803',
                  'def_headers' => undef,
                  'parse_head' => 1,
                  'proxy' => {},
                  'max_size' => undef
                }, 'LWP::UserAgent' );

Since a 302 means a redirect is being requested, and
'requests_redirectable' only contain GET and HEAD requests, possibly the
POST isn't seen as being redirecable. Maybe adding 'POST' to that
attribute, or possibly doing a GET will resolve it.