Find empty value inside array

Let's say I have the item:

(set: $knife to (datamap:
"Name","Knife",
"Description","a simple knife",
"equip", false)
)
(set: $iknife to "(link-reveal: 'knife')[(set: $myeq to it + (a: $knife))]")

And an array to store my items:

(set: $myeq to (a:))

It will be stored inside my array, like:

(set: $myeq to (a: $knife, $otheritem, $etc)

But if my array have an empty value, like:

(set: $myeq to (a: $knife), "", $otheritem, $etc, "", "")

How could I make the item be stored in one of this spaces? Do Harlowe has any sort of foreach or any other loop?