* Regex vector selection on a hierarchical circuit (cf. user_examples/two_balance).
* Two instances X1, X2 of a stage -> internal nodes appear as x1.n1, x2.n1, ...
Vin in 0 DC 3
X1 in  mid stage
X2 mid out stage
RL out 0 1k
.subckt stage a z
  R1 a  n1 1k
  R2 n1 n2 1k
  R3 n2 z  1k
.ends
.op
.control
  run
  echo "--- display x1.*   (just X1's two internal nodes) ---"
  display x1.*
  echo "--- print \"x1.*\"   (their node voltages) ---"
  print "x1.*"
  echo "--- unlet x2.* ; then display .*n1  (x2.n1 now gone) ---"
  unlet x2.*
  display .*n1
.endc
.end