Ansible cannot iterate on a dict & check the results (changed_when/failed_when/&c).

broken.yaml

---
- hosts: localhost
  vars:
    places:
      alpha: /home
      beta: /srv
      delta: /opt
      gamma: /etc
      epsiolon: /code

  tasks:
  - stat:
     path: '{{ places[item] }}'
    with_items: '{{ places.keys() }}'
    register: places_stats

  - debug:
      msg: 'it doesnt exist'
    when: not item.stat.exists
    with_items: '{{ places_stats.results }}'