如何用其他占位符替换模板中的占位符

Question

这是我的模板，其中包含一些要替换的占位符：

{{ __PLACEHOLDER1__ }} to test.
{{ __PLACEHOLDER2__ }} to test.
{{ __PLACEHOLDER3__ }} to test.

以下是包含这些占位符值的yaml文件：

__PLACEHOLDER1__: placeholder replaced 1
__PLACEHOLDER2__: placeholder replaced 2
__PLACEHOLDER3__: placeholder replaced 3

最后是我的剧本：

- hosts: localhost
  become: true
  become_method: sudo
  become_user: "{{ deployer }}"

  vars:
    ansible_become_pass: "{{ deployer_pass }}"
    root_dir: "."

  vars_files:
    - "{{ deployer_sec }}"
    - "{{ placeholder_vals }}"

  tasks: 
    - name: 'Grab files with placeholders in {{ root_dir }}'
      find:
        pattern: "*.template"
        path: "{{ root_dir }}"
        recurse: yes
      register: files_with_placeholders
    - name: 'Replace placeholders'
      template:
        src: "{{ item.path }}"
        dest: "{{ (item.path | splitext)[0] }}"
      with_items: "{{ files_with_placeholders.files }}"

到目前为止很好...但是如果我有这样的模板怎么办：

{{ PLACEHOLDER1 }} to test.
{{ PLACEHOLDER2 }} to test.
{{ PLACEHOLDER3 }} to test.

在运行我的剧本之前，我需要转换模板中的占位符以匹配yaml文件中定义的变量：

{{ PLACEHOLDER1 }} should become {{ __PLACEHOLDER1__ }}
{{ PLACEHOLDER2 }} should become {{ __PLACEHOLDER1__ }}
{{ PLACEHOLDER3 }} should become {{ __PLACEHOLDER1__ }}

在处理模板之前，如何用新的占位符替换原始占位符？