- name: just plain order
  hosts: all
  gather_facts: false
  order: '{{ myorder|default("inventory")}}'
  tasks:
    - shell: echo '{{inventory_hostname}}' >> hostlist.txt

- name: with serial
  hosts: all
  gather_facts: false
  serial: 1
  order: '{{ myorder|default("inventory")}}'
  tasks:
    - shell: echo '{{inventory_hostname}}' >> shostlist.txt

- name: ensure everything works
  hosts: localhost
  gather_facts:  false
  tasks:
    - assert:
        that:
          - item.1 == hostlist[item.0]
          - item.1 == shostlist[item.0]
      loop: '{{ lookup("indexed_items", inputlist) }}'
      vars:
        hostlist: '{{lookup("file", "hostlist.txt").splitlines()}}'
        shostlist: '{{lookup("file", "shostlist.txt").splitlines()}}'