ansible variable basing on hostname's suffix - ansible

Question

I need to create a user on a system depending on it's function (test or production)
Test systems are named with suffix -tXX while prod ones are with -pXX (where XX is two digits numbering).
in variable file I have set:
auser: "{{ 'usertest' if {{ ansible_hostname|lower }} | regex_search('t[0-9]{2}$') else 'userprod' }}"
the error I get is during playbook run is:
fatal: [192.168.1.10]: FAILED! => {"msg": "An unhandled exception occurred while templating '{{ 'usertest' if {{ ansible_hostname|lower }} | regex_search('t[0-9]{2}$') else 'userprod' }}'. Error was a <class 'ansible.errors.AnsibleError'>, original message: template error while templating string: expected token ':', got '}'. String: {{ 'usertest' if {{ ansible_hostname|lower }} | regex_search('t[0-9]{2}$') else 'userprod' }}"}
Complete playbook is:
---
- hosts: testgrp
become: yes
vars:
- auser: "{{ 'usertest' if {{ ansible_hostname|lower }} | regex_search('t[0-9]{2}$') else 'userprod' }}"
tasks:
- name: Add groups
group:
name: "{{ item.name }}"
gid: "{{ item.gid }}"
state: present
loop:
- { name: 'group1', gid: '1101' }
- { name: 'group2', gid: '1102' }
- { name: 'group3', gid: '1103' }
- name: Add users
user:
name: "{{ item.name }}"
group: "{{ item.group }}"
groups: "{{ item.groups }}"
state: present
loop:
- { name: "{{ auser }}", group: 'group1', groups: 'group2,group3', uid: '1101' }

Answer 1

For example
- hosts: srv-t01,srv-p01
gather_facts: false
vars:
auser: "{{ inventory_hostname | lower is match('^.*-t[0-9]{2}$') |
ternary('usertest', 'userprod') }}"
tasks:
- debug:
var: auser
gives
ok: [srv-t01] =>
auser: usertest
ok: [srv-p01] =>
auser: userprod
A more robust solution is to select an index, e.g. the play below gives the same result
- hosts: srv-t01,srv-p01
gather_facts: false
vars:
auser_dict:
t: usertest
p: userprod
aindex: "{{ inventory_hostname | lower |
regex_replace('^.*-(.+)[0-9]{2}$', '\\1') }}"
auser: "{{ auser_dict[aindex] }}"
tasks:
- debug:
var: auser