using ansible variable in task conditonal - ansible

Question

When I use an Ansible variable in the failed_when conditional, Ansible complains and fails by telling me that I cannot use Jinja2 expressions with failed_when.
Below snippet does not work:
vars:
var1: "var"
tasks:
- name: "sth"
raw: "anothersth"
register: status
failed_when: var1 in status.stdout
I want to use a regex in the above example and use variable var1 within a regex. This also fails.
I want to fail the task if var1 is repeated in the beginning and at the end of the stdout_lines. I was thinking something like this:
failed_when: regex("^{{var1}}/.*/{{var1}}$") in status.stdout
I wonder whether there is a way to achieve what I intend to do?
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Exact play and the description:
Let me explain what I am trying to do:
run a command with "raw" module and register the stdout_lines.
iterate over a list of items, where list is a fact of current ansible host
use failed_when to search a pattern in the registered stdout and fail the task if it is not found
peers_underlay is a list defined in the host file:
peers_underlay:
- ip: "172.16.1.2"
- ip: "172.16.1.6"
This is the play:
- hosts: leaf-2, spine-1
gather_facts: no
tags: [ verify ]
vars:
bgp_underlay: "show ip bgp summary"
tasks:
- name: "underlay bgp test"
raw: "{{ bgp_underlay }}"
register: underlay_status
with_items: "{{ peers_underlay }}"
failed_when: not regex(".*/{{ item['ip'] }}/.*/Estab/.*") in underlay_status.stdout_lines

Answer 1

Q: "Fail the task if var1 is repeated in the beginning and at the end."
A: It's possible to test strings. For example, use regex
- hosts: localhost
vars:
my_stdout1: 'ABC dlkjfsldkfjsldkfj ABC'
my_stdout2: 'alkdjflaksdjflakdjflaksjdflaksdjflasj'
var1: 'ABC'
my_regex: '^{{ var1 }}(.*){{ var1 }}$'
tasks:
- debug:
msg: my_regex match my_stdout1
when: my_stdout1 is regex(my_regex)
- debug:
msg: my_regex match my_stdout2
when: my_stdout2 is regex(my_regex)
gives
"msg": "my_regex match my_stdout1"
The particular task sequence would be
vars:
var1: "var"
my_regex: '^{{ var1 }}(.*){{ var1 }}$'
tasks:
- name: "sth"
raw: "anothersth"
register: status
failed_when: status.stdout is regex(my_regex)