You have an array and you want to seperate by a batch of 3

/*
You have an array and you want to seperate by a batch of 3
E.g
Array: {"a", "b", "c", "d", "e", "f", "g", "h"}
Expected output: { ["a", "b", "c"], [ "d", "e", "f"], ["g", "h"] }
*/

a!localVariables(
  local!chunkSize: 3,
  local!startingList: { "a", "b", "c", "d", "e", "f", "g", "h" },
  local!wholeListSize: length(local!startingList),
  local!numChunks: ceiling(local!wholeListSize / local!chunkSize),
  local!data: a!forEach(
    enumerate(local!numChunks),
    a!localVariables(
      local!currentStartIndex: fv!item * local!chunkSize + 1,
      /* note: this utilizes zero-index of fv!item */
      local!currentIndices: enumerate(local!chunkSize) + local!currentStartIndex,
      /* this rule just unions the input array with itself and rejects null values */
      reject(
        fn!isnull,
        index(
          local!startingList,
          local!currentIndices,
          null()
        )
      )      
    )
  ),
  local!data
)