Warning: Variable tail only occurs once in file subsumption.dl at line 91
   list = [i, tail],
--------------^------
Warning: Variable l1 only occurs once in file subsumption.dl at line 92
   i = [l1, u1],
--------^--------
Warning: Variable u2 only occurs once in file subsumption.dl at line 93
   y = [l2, u2],
------------^----
Warning: Variable tail only occurs once in file subsumption.dl at line 112
   list = [i, tail],
--------------^------
Warning: Variable u2 only occurs once in file subsumption.dl at line 114
   y = [l2, u2],
------------^----
Warning: Variable tail only occurs once in file subsumption.dl at line 124
   list = [i, tail],
--------------^------
