main.yml

# tasks/main.yml
- include: normal_user.yml
  with_items: "{{ users }}"
  loop_control:
    loop_var: outer_users

normal_user.yml

# tasks/normal_user.yml
- name: "create normal user {{ outer_users.name }}"
  become: true
  user:
    name: "{{ outer_users.name }}"
    createhome: "{{ outer_users.createhome | default(yes) }}"
    shell: "{{ outer_users.shell | default('/bin/bash') }}"
    state: present
  register: user_created
  ignore_errors: true
  tags:
    - user
# Using 'other_users' in subsequent tasks gives an error. See output
- debug:
    msg: "Can't create user {{ other_users.name }} on this host using module 'user'. Trying it manually."
  when: user_created|failed
  tags:
    - user,"{{ other_users.name }}"

- include: add_manual.yml
  when: user_created|failed

output

ERROR! 'outer_users' is undefined

vars_main.yml

# vars/main.yml
users:
  - hodor:
    name: test
    createhome: yes
    shell: /bin/bash
    state: present