Access Middleman template vars from a helper

Say you pass a local variable to a Middleman template via something like proxy:

proxy('/someplace/nice', 'nice.html', :locals => { :foo => 'boop' })

And you want to use :foo inside a helper without manually passing the variable as an argument. Turns out local variables are accessible in all helpers via current_page.metadata[:locals]:

helpers do
  def helpyhelp
    foo = current_page.metadata[:locals][:foo]
  end
end