Kubernetes If/Or Statement in Configmap

Im trying to write an IF statement in my configmap but I cannot find any sites that combine and IF statement with OR. For example:

      <% if @project_name == 'site-a' || 'site-b' %>
      security:
        default-groups:
          - reader # Read only for everybody
      <% end %>

Would this be accurate? Ideally, if the variable is called site a or site b. I can probably do an else block but it's not necessary.

Thanks.