VARIABLE IS NOT DEFINED when trying to register output in playbook - ansible

Question

I'm trying to register a variable with the output to a query of a F5 pool and I'm getting this error:
"<type 'list'>": "VARIABLE IS NOT DEFINED!",
What is that I'm doing wrong?
Any help appreciated.
Thanks!
---
- name: GRAB F5 FACTS
hosts: f5
connection: local
gather_facts: no
tasks:
- name: Collect BIG-IP facts
bigip_device_facts:
gather_subset: ltm-pools
provider: "{{ prov }}"
register: bigip_device_facts
- name: FACTS OUTPUT
debug:
var: "{{ item.members | rejectattr('state', 'match', '^present$') | map(attribute='name') | list }}"
register: jkout
with_items: "{{ bigip_device_facts.ltm_pools }}"
when: item.full_path == "/Common/mypool"
- name: Set a variable
debug:
msg: "jkvar={{ jkout }}"

Answer 1

You are using the debug: module with the option var: and this expects a variable, not a jinja2 template.
So either change it to:
debug:
var: item.members
or
debug:
msg: "{{ item.members }}"

Answer 2

Like said by #dgw, the problem is with the var option of debug module.
https://docs.ansible.com/ansible/latest/modules/debug_module.html#parameters
This playbooks works:
- name: test rejectattr
hosts: localhost
gather_facts: no
vars:
members:
- { name: "one", state: "present" }
- { name: "two", state: "absent" }
- { name: "three", state: "present" }
tasks:
- name: FACTS OUTPUT
debug:
msg: "{{ members | rejectattr('state', 'match', '^present$') | map(attribute='name') | list }}"

Answer 3

Thanks for your responses. I'll investigate it further.
Apart from that, I think I've been able to solve it another way.
- name: FACTS OUTPUT
set_fact:
listado: "{{ item.members | rejectattr('state', 'match', '^present$') | map(attribute='name') | list }}"
with_items: "{{ bigip_device_facts.ltm_pools }}"
when: item.full_path == "/Common/mypool"
- debug: msg={{ listado }}
register: jkout
- name: Set a variable
debug:
msg: "jkvar={{ jkout }}"
Is that a right way to do it?
Thanks!!