#!/usr/bin/env perl
use WWW::Mechanize;
use HTTP::CookieJar::LWP ();
use IO::Socket::SSL qw();

my $uri ="https://sso.employer.com/serviceredirect/login?service=https://actualserviceurl.employer.com/my/service";

my $username = "username";
my $password = q(password);

my $fields = {
    username    => $username,
    password => $password,
};

my $m = WWW::Mechanize->new( cookie_jar => $cookie_jar, autocheck => 1, ssl_opts => { SSL_verify_mode => IO::Socket::SSL::SSL_VERIFY_NONE, verify_hostname => 0 }, env_proxy => 1, keep_alive => 1, timeout => 30, agent => 'myagent' );

$m->max_redirect(2);
my $content = $m->post($uri);

$m->submit_form(
    form_number => 1,
    fields      => $fields,
    button      => 'submit'
);

print $content->headers()->as_string;

##</code><code>##

POST https://sso.employer.com/serviceredirect/login?service=https://actualserviceurl.employer.com/my/service
Accept-Encoding: gzip
User-Agent: myagent
Content-Length: 0
Content-Type: application/x-www-form-urlencoded

(no content)
HTTP/1.1 200 OK

[...]

HTTP/1.1 302 Found
Cache-Control: no-cache, no-store, max-age=0, must-revalidate
Date: Fri, 22 Nov 2019 13:20:31 GMT
Pragma: no-cache
Via: 1.1 login.1and1.org
Location: https://actualserviceurl.employer.com/my/service?ticket=xxxsuperlonggeneratedticketidxxx

[...]