Let's say you have a template file named my_file.j2.

/path/to/templates/my_file.j2

And let's say my_file.j2 contains the following.

{%Y}

And you have the following playbook which uses templates to copy my_file.j2 to /tmp/my_file.txt on each target server.

---
- hosts: all
  tasks:
  - name: copy my_file.j2 to /tmp/my_file.txt
    template:
      src: /path/to/templates/my_file.j2
      dest: /tmp/my_file.txt
...

Running this play should return Encounted unknown tag 'Y' because {%Y} is built in jinja2 syntax.

Encounted unknown tag 'Y'

In this scenario, you can wrap {% raw %} and {% endraw %} around the {%Y} built in jinja2 syntax so that {%Y} is not interpreted as jinja2.

{% raw %}{%Y}{% endraw %}