ansible_role_monitored/tasks/packages.yml

---
- name: Install Monitoring-Plugins
  package:
    name: "{{ monitored_packages_mp }}"
    state: latest
  register: monitoringplugins
  ignore_errors: True

- name: Install Nagios-Plugins
  package:
    name: "{{ monitored_packages_np }}"
    state: latest
  when: monitoringplugins is failed

- name: Install additional packages
  package:
    name: "{{ monitored_packages_additional }}"
    state: latest
  when: monitored_packages_additional|bool