%%HP: T(3)A(R)F(.);
\<< 1 \->LIST
  DO DUP
    \<< GF
    \>> MAP 1
    \<< OBJ\-> DROP
    \>> DOSUBS
  UNTIL DUP2 SAME ROT
DROP
  END
  IF DUP SIZE 1 ==
  THEN HEAD
  ELSE \PILIST
  END
\>>