While reviewing code the other day, I came across the following snippet (here converted to a procedure).
Ds := proc(V::set, n::posint, t)
local i,v;
{seq(seq((D@@i)(v)(t), i=1..n), v in V)};
end proc:
The purpose of this is to generate a set of derivatives at a point of a set of unassigned names. For example
Ds({x,y},2,0);
 ...