[racket] `namespace-set-variable-value!` doesn't "shadow"? How to do?

Continuing my rendition of Billy Idol's Dancing with Myself...

OK I got it to work like so:

-- pre-base.rkt --
(module pre-base racket/base
  (provide (except-out (all-from-out racket/base) date)))

-- template.rkt --
#lang racket/base

(module template "pre-base.rkt"
  (provide render-template)
  (define (render-template dir filename dict)
  ... as before ...)

(require 'template)
(provide render-template)
------

I couldn't figure out how to do it in one file (without a separate
"pre-base.rkt" file). If anyone knows how, I'm curious. Otherwise not
a big deal, I think I'm all set.

---------------------------------------------------
"On the floors of Tokyo
Down in London town's a go-go
With the record selection
And the mirror's reflection
I'm a-dancing with myself"