---

- name: 'Variable in templates: a template can use a variable from task or playbook but not from an outter template'
  gather_facts: no
  hosts: localhost
  vars: 
    input: 'OK'
  tasks:
  - block:
    - debug:
        var: output
    - assert:
        that:
        - output == "OKKOOK"
    vars:
      output: "{{ lookup('template', 'template.j2') }}"