--- esY.py-	2016-09-11 01:00:00.000000000 +0900
+++ esY.py	2016-09-11 02:00:00.000000000 +0900
@@ -128,6 +128,8 @@ def tstk_pop_ret(v):
 	return v
 
 def ops_idx(ops, term, op):
+	if type(op) == tuple and op[1] == 'back':
+		op = op[0]
 	i = next( ( i for (i, (term_, bind, lst)) in enumerate(ops) if term_ == term and op in lst ), None )
 	if i is None:
 		print yaml.dump(tstk)