ansible - example of multiple plays, one creating a new group

main.yml

# roles/do_something/tasks/main.yml
---
- name: do something
  command: grep foo /tmp/bar
  register: result
    
- name: add host to new group based on result
  add_host: hostname=inventory_hostname group_name=mynewgroup
  when: result.stdout == 'whatever'

newgroup.yml

#  roles/do_something/tasks/newgroup.yml
---
- name: do something
  ...

play.yml

---
- hosts: somegroup
  roles:
    - do_something

- hosts: mynewgroup
  tasks:
    - include: roles/do_something/tasks/newgroup.yml