%
% eliminate values not in exempt list
%
% stack: empty [ . . . ] val1
%
% perform for current node's descendants, not current node
%
empty
{
 exch isnull ?
 escape
 ^"|" &" " &
} loop
pop

!filter
%
% determine the last node in the contiguous section of nodes
% this is the last descendant (last child of last child of . . .)
%
% stack:
%
 _\
 dup
 {
  "Below" get zero ?
  dup !\
 } loop
 pop
%
% stack: parent
%
 + 1 _\
 {
  dup !\ @^*Values
  execstr -2 1
  {
   pop
   dup escape _filter <> not
   {
    false second _\ "Valued" set
   } if
   pop2
  } for
 } for
%
% stack:
%