reader fails on `(return null)`

index2.esl

(var myState (object inArray false))
(var myStack (array))

(var rxOpenBracket (regex ^\\[))
(var rxCloseBracket (regex \\]$))


(var strTail
 (function (s)
  (return ((. s substring) 1))))
(var strAllButLast
 (function (s)
  (return ((. s substring) 0 (- (. s length) 1)))))

(var transform
     (function
      (node)

      (if (instanceof node Array)
        ;; is array
        (block
         (return ((. node map) (function (y) (return (transform y))))))
        
        ;; non array
        (block
         (if (|| (== (typeof node) "string")
                 (== (typeof node) "number"))
           
           (block
            (if (. myState inArray)
              (block
               ((. myStack push) node)

               ;; ========================================
               ;; exception on (return null)
               ;; ========================================
               (return "")
               )
              (return node)))
           
           (block
            (var s (. node atom))
            (if ((. rxOpenBracket test) s)
              (block
               ;; got open array
                     
               ;; special case
               (if (== s "[]")
                 (return (array (object atom "array"))))
                     
               (= (. myState inArray) true)
               ;; start making the array
               ((. myStack push) (object atom "array"))

               (if (< 1 (. s length))
                 (block
                  ;; this will push from the inner recursion!!!
                  (transform (eval (strTail s)))))

               ;; ========================================
               ;; exception on (return null)
               ;; ========================================
               (return "")))

            (if ((. rxCloseBracket test) s)
              (block
               (= (. myState inArray) false)
               ;; last atom is more than just a bracket
               (if (< 1 (. s length))
                 ((. myStack push) (eval (strAllButLast s))))
                     
               ;; clone buffer + empty the global stack
               (var rtn ((. myStack slice) 0))
               (= myStack (array))
                     
               (return (transform rtn))
                     
               )
              )

            (return (object atom (. node atom))))))
        
        )))


(= (. module exports)
   (function
    ()
    (var args ((. Array prototype slice call) arguments 0))
    (return ((. this multi apply) null ((. args map) transform)))))

makefile

export PATH := node_modules/.bin:$(PATH)

index2.js: index2.esl
	eslc < $< > $@

test2.js: test2.esl
	eslc < $< > $@

test2: index2.js test2.js
	node test2.js

test2.esl

(var runTest (function (name func)
 ((require "tape") name
                   (function (t)
                             (func t)
                             ((. t end)))))) ; Automatically end tests

(var eslc
 (function (code)
           (var fullCode ; wrap in a call
                (+ "(macro xfm (require \"./index2.js\")) (xfm "
                   code
                   ")"))
           (return ((require "eslisp") fullCode))))

(macro test
 (function (name body)
  (return `(runTest ,name (function (t) ,@body)))))

(test "hello"
      (((. t equals) (eslc "1") "1;")))

(test "common vector"
      (((. t equals) (eslc "[1 2 3]")  
        "'';\n'';\n[\n    1,\n    2,\n    3\n];")))