Variable List can be bound to another list.

The function mustache:compiler/2 generate a complex structure of fun out of the template. When you have a template like this one:
{{#apis}}
 {{url}}
    {{#method}}
      {{stuff}}
    {{/method}}
{{/apis}}

... and apis and methods are different lists, the method will generete a error message. This is a small demonstration of the problem:

(fun() -> List = a, (fun() -> List = b, List end)() end)(). 

This pull request might not be the best solution, but I hope it works.