Reduce method invocations and object allocations in head()

actionpack/lib/action_controller/metal/head.rb

@@ -29,7 +29,7 @@ def head(status, options = {})
       content_type = options.delete(:content_type)
 
       options.each do |key, value|
-        headers[key.to_s.dasherize.split("-").each { |v| v[0] = v[0].chr.upcase }.join("-")] = value.to_s
+        headers[key.to_s.split(/[-_]/).each { |v| v[0] = v[0].upcase }.join("-")] = value.to_s
       end
 
       self.status = status