@(collect)
@  (coll)@{item /[^$]+/}@(end)
@(end)
@; nc = number of columns
@; pi = padded items (data with row lengths equalized with empty strings)
@; cw = vector of max column widths
@; ce = center padding
@(bind nc @[apply max [mapcar length item]])
@(bind pi @(mapcar (op append @1 (repeat '("") (- nc (length @1)))) item))
@(bind cw @(vector-list
             (mapcar (op apply max [mapcar length @1])
                     ;; matrix transpose trick cols become rows:
                     [apply mapcar [cons list pi]])))
@(bind ns "")
@(output)
@  (repeat)
@    (rep :counter i)@{pi @[cw i]} @(end)
@  (end)
@  (repeat)
@    (rep :counter i)@{pi @(- [cw i])} @(end)
@  (end)
@  (repeat)
@    (rep :counter i)@\
     @{ns @(trunc (- [cw i] (length pi)) 2)}@\
     @{pi @(- [cw i] (trunc (- [cw i] (length pi)) 2))} @(end)
@  (end)
@(end)