Adding to header using module-define! and alist with markups

[Nate Whetsell]

I’m trying to programmatically add items to score headers from an alist. This 
works when an item consists of just a string. I can’t seem to get this to work 
when an item is a markup, no matter how the markup is entered. Is there some 
way to store markups in an alist, and then use those markups in a header?

Below is an example illustrating the issue I’m having. Any help would be 
greatly appreciated!

Thanks,
Nate

```
\version "2.22.0"

\paper {
  scoreTitleMarkup = \markup {
    \column {
      \fromproperty #'header:piece
      \justify-field #'header:instruction
    }
  }
}

#(define instructions '(
  ; Using a LilyPond code block does not work.
  (1 . #{
    \markup {
      "Does not work"
      \score {
        \new Staff { c'1 }
        \layout { ragged-right = ##t indent = 0 }
      }
    }
  #})
  ; Using the Scheme form of a markup expression does not work.
  (2 . (markup #:line (#:simple "Does not work")))
  ; Using a string works.
  (3 . "Works")))

\book {
  #(do ((study-number 1 (1+ study-number)))
      ((> study-number 3))
    (let ((header (make-module)))
      (module-define! header 'piece (number->string study-number))
      (let* (
          (instruction (assoc study-number instructions))
          (score (scorify-music #{ { c'1 } #})))
        (begin
          (if instruction (module-define! header 'instruction (cdr 
instruction)))
          (ly:score-set-header! score header)
          (add-score score)))))
}
```