upcase.rb

def deep_upcase(item)
  if item.respond_to? :upcase
    return item.upcase
  end
  case item
  when Array
    item.map { |i| deep_upcase(i) }
  when Hash
    Hash[item.map { |k,v| [deep_upcase(k), deep_upcase(v)] } ]
  else
    item
  end
end
Puppet::Parser::Functions.newfunction(:upcase, :type => :rvalue) do |args|
  deep_upcase(args[0])
end

Realistically we can just do the same pattern to upcase instead of creating a new function that goes further but like the recursion

The benefit to having the recursive function be a separate function is that then you can perform validation on the top-level object passed in and not on what's contained inside it, so upcase(4) is invalid but upcase({'a' => 4}) would still work.