---
- hosts: all
  gather_facts: false
  vars:
    local_group_info:

      - name : developer group
        which_users  :
          - mike
          - george
        which_groups :
          - adm
          - www-data
        on_hosts  :
          - test.sv1.org
          - punchy.sv1.org

      - name: admin group
        which_users:
          - kelly
        which_groups:
          - sudo
        on_hosts  :
          - test.sv1.org

  tasks:
    - name: Add users to local groups if current host matches
      when: inventory_hostname in item.0.on_hosts or 'all' in item.0.on_hosts
      debug:
        msg: "user {{ item.0.which_users }} should be in group {{ item.1 }}"
      with_subelements:
        - "{{ local_group_info }}"
        - which_groups

PLAY [all] **************************************************************************************************************************

TASK [Add users to local groups if current host matches] ****************************************************************************
ok: [test.sv1.org] => (item=[{u'which_users': [u'mike', u'george'], u'name': u'developer group', u'on_hosts': [u'test.sv1.org', u'punchy.sv1.org']}, u'adm']) => {
    "msg": "user [u'mike', u'george'] should be in group adm"
}
ok: [test.sv1.org] => (item=[{u'which_users': [u'mike', u'george'], u'name': u'developer group', u'on_hosts': [u'test.sv1.org', u'punchy.sv1.org']}, u'www-data']) => {
    "msg": "user [u'mike', u'george'] should be in group www-data"
}
ok: [test.sv1.org] => (item=[{u'which_users': [u'kelly'], u'name': u'admin group', u'on_hosts': [u'test.sv1.org']}, u'sudo']) => {
    "msg": "user [u'kelly'] should be in group sudo"
}

PLAY RECAP **************************************************************************************************************************
test.sv1.org       : ok=1    changed=0    unreachable=0    failed=0