Added more test cases

re_test.go

@@ -35,6 +35,11 @@ var reTests = []struct {
 	{"ab?", "ab", []matchIndex{{0, 2}}},
 	{"a?b", "ab", []matchIndex{{0, 2}}},
 	{"a?", "", []matchIndex{{0, 0}}},
+	{"a?b?c", "a", []matchIndex{}},
+	{"a?b?c?", "ab", []matchIndex{{0, 2}}},
+	{"a?b?c?", "ac", []matchIndex{{0, 2}}},
+	{"a?b?c", "abc", []matchIndex{{0, 3}}},
+	{"a?b?c", "acb", []matchIndex{{0, 2}}},
 }
 
 func TestFindAllMatches(t *testing.T) {