[root@websrv01 ansible]# cat hosts

[app]
localhost

[app_bla]
localhost
[root@websrv01 ansible]# cat version
app:
  - name: bla
    version: 1

app_bla:
  - name: blub
    version: 1
[root@websrv01 ansible]# cat play.yml
- hosts: app:app_bla
  remote_user: root
  pre_tasks:
  - include_vars: version
  tasks:
  - debug: var="{{item}}"
    with_items: group_names
  - debug: msg="going to install {{ hostvars[inventory_hostname][item]}} on {{inventory_hostname}}"
    with_items: group_names
    when: hostvars[inventory_hostname][item] is defined
[root@websrv01 ansible]# ansible-playbook play.yml

PLAY [app:app_bla] *************************************************************

TASK [setup] *******************************************************************
ok: [localhost]

TASK [include_vars] ************************************************************
ok: [localhost]

TASK [debug] *******************************************************************
[DEPRECATION WARNING]: Using bare variables is deprecated. Update your playbooks so that the environment value uses the full variable syntax
('{{group_names}}').
This feature will be removed in a future release. Deprecation warnings can be disabled by setting deprecation_warnings=False in
ansible.cfg.
ok: [localhost] => (item=app) => {
    "app": [
        {
            "name": "bla",
            "version": 1
        }
    ],
    "item": "app"
}
ok: [localhost] => (item=app_bla) => {
    "app_bla": [
        {
            "name": "blub",
            "version": 1
        }
    ],
    "item": "app_bla"
}

TASK [debug] *******************************************************************
[DEPRECATION WARNING]: Using bare variables is deprecated. Update your playbooks so that the environment value uses the full variable syntax
('{{group_names}}').
This feature will be removed in a future release. Deprecation warnings can be disabled by setting deprecation_warnings=False in
ansible.cfg.
ok: [localhost] => (item=app) => {
    "item": "app",
    "msg": "going to install [{u'version': 1, u'name': u'bla'}] on localhost"
}
ok: [localhost] => (item=app_bla) => {
    "item": "app_bla",
    "msg": "going to install [{u'version': 1, u'name': u'blub'}] on localhost"
}

PLAY RECAP *********************************************************************
localhost                  : ok=4    changed=0    unreachable=0    failed=0