ansible_custom_template.yml

---
##
# Invoke any type of script to modify files. Dry-run friendly usually.
# remote_path: Path to file on server.
# script:      Commands that returns altered content on stdout
##

- name: get current content
  always_run: yes
  register: remote
  slurp: src={{ remote_path }}

- name: modify contents
  register: modified
  delegate_to: localhost
  become: no
  always_run: yes
  changed_when: no
  shell: echo {{ remote.content }} | base64 -D | {{ script }}

- name: replace contents
  copy:
    content: '{{ modified.stdout }}'
    dest: '{{ remote_path }}'