How to reference a variable using the builtin vars plugin?

Question

Is it possible to reference a variable in a task using the builtin vars plugin?

When I use the "{{ variable }}" syntax it is treated like a string.

- name: Get the active network interface name
  shell: ip route get 1.1.1.1 | grep -Po '(?<=dev\s)\w+' | cut -f1 -d ' '
  register: interface_name
  
  ## Example: interface_name: enp33s0f0

- name: Update netplan
  set_fact:
    mydata: "{{ mydata | combine(newdata, recursive=True) }}"
  vars:
    newdata:
      network:
        ethernets:
          "{{ interface_name.stdout }}":
            dhcp4: true
            critical: true
            nameservers:
              addresses: 
              - 2.2.2.2
              search: [test.local]

- name: Write back to a file
  copy:
    content: "{{ mydata | to_nice_yaml }}"
    dest: /etc/netplan/00-installer-config.yaml
  register: update

cat 00-installer-config.yaml

network:
    ethernets:
        '{{ interface_name.stdout }}':
            critical: true
            dhcp4: true
            nameservers:
                addresses:
                - 2.2.2.2
                search:
                - test.local

If this is not possible is there an alternative?