gistfile1.txt

---
- hosts: localhost
  connection: local

  vars:
    fake_group_names:
    - web
    - db

  tasks:

  - debug: msg="should match"
    when: '"web" in fake_group_names or "foo" in fake_group_names'

  - debug: msg="should not match"
    when: '"foo" in fake_group_names or "bar" in fake_group_names'

gistfile2.txt

Timothys-MacBook-Pro:ansible-test tgerla$ ansible-playbook -i localhost, test-in.yml

PLAY [localhost] **************************************************************

GATHERING FACTS ***************************************************************
ok: [localhost]

TASK: [debug msg="should match"] **********************************************
ok: [localhost] => {
    "msg": "should match"
}

TASK: [debug msg="should not match"] ******************************************
skipping: [localhost]

PLAY RECAP ********************************************************************
localhost                  : ok=2    changed=0    unreachable=0    failed=0