LFUN
  void SetExtra (mixed name, mapping|closure data)

DESCRIPTION
  Store data in this objects P_EXTRA_DESC.

  Arguments:
    name: the key value to store the data under.
    data: the data to store, either a mapping or a closure returning a
          mapping.

  The function stores <data> as P_EXTRA_DESC[<key>].

EXAMPLE
  SetExtra("my data", ([ P_SHORT:({ "(worn)" }) ]));

IMPLEMENTED
  /std/thing/description