Here’s a little Twine thought exercise. Let’s say you want to output elements from an array in a random order, with none of them being reused.

First, we set up an array containing our random elements:

(set: $a to (array: "first", "second", "third", "fourth"))

Then, we pick a random number to index that array with, and use it to output that array’s element – or do whatever it is we want to do to it. We could use (goto:) to send the player to a named passage; thus creating a kind of randomly-generated maze.

(set: $r to (random: 1, $a's length))
(print: $a's $r)

Point of note: array referencing in Twine2’s Harlowe is done with array's first, array's second, array's nth, but you can also just say array's n, as above. I wasn’t sure if that was going to work, but it does.

Next, we use (move:) to move the item from our array into another variable (which we don’t care about). This will update the array so that the randomly indexed element is no longer present.

(move: $a's $r into $trash)

Note: As of September 2015, be careful to use into and not to in the (move:) function. Using to will set the indexed value to 0, and not remove it from the array. This is a known bug.

You can test $a's length to see how many elements are left, and if the length is zero you know you have dealt with the entire list.