the same cell as [1 2 3], written out.
[1 2 3]
:* makes a tuple of many elements, nesting to the right.
:*
:*(1 2 3) is [1 2 3].
:*(1 2 3)
irregular forms:
[a b c d] is :*(a b c d)
[a b c d]
:*(a b c d)