Install Erlang and Elixir.

playbook.yml

---
- hosts: builders
  tasks:
    - name: Fetch Erlang Solutions repository
      get_url:
        url: https://packages.erlang-solutions.com/erlang-solutions_1.0_all.deb
        dest: /tmp/erlang-solutions_1.0_all.deb
    - name: Add Erlang Solutions repository
      become: true
      apt:
        deb: /tmp/erlang-solutions_1.0_all.deb
    - name: Install Erlang
      become: true
      apt:
        update_cache: yes
        name: esl-erlang=1:19.2
        state: present
    - name: Install Elixir
      become: true
      apt:
        name: elixir=1.4.0-1
        state: present

pretty straightforward!