A description list, consisting of a number of pairs of a `description term', dt, and `description data', dd. Notionally, the dd is the definition of a term introduced by the dt, but the construction can legitimately be used a little more widely than this.
dl |_(update*, |__(dt, |___dd)+)
A hint to the formatter, suggesting that the contents of the list might benefit from a more compact representation. As a hint, the formatter is free to ignore it.