diff --git a/t_parser_test.go b/t_parser_test.go
index f621502..0ae7839 100644
--- a/t_parser_test.go
+++ b/t_parser_test.go
@@ -135,6 +135,12 @@ func TestGeneralParser(t *testing.T) {
 		/* 121 */ {`1+1|2+0.5`, float64(2), nil},
 		/* 122 */ {`1.2()`, newFraction(6, 5), nil},
 		/* 123 */ {`1|(2-2)`, nil, `division by zero`},
+		/* 124 */ {`x="abc"; x ?! #x`, int64(3), nil},
+		/* 125 */ {`x ?! #x`, nil, `[1:7] prefix/postfix operator "#" do not support operand '<nil>' [nil]`},
+		/* 126 */ {`x ?! (x+1)`, nil, nil},
+		/* 127 */ {`"abx" ?! (x+1)`, nil, `[1:6] left operand of "?!" must be a variable`},
+		/* 128 */ {`"abx" ?? "pqr"`, nil, `[1:6] left operand of "??" must be a variable`},
+		/* 129 */ {`"abx" ?= "pqr"`, nil, `[1:6] left operand of "?=" must be a variable`},
 	}
 
 	// t.Setenv("EXPR_PATH", ".")