China DOS Union

In pure DOS mode, the following statements can't be used:
set /p confrim=yes or no?(y/n):
if %confirm% == y goto ..
if %confirm% == n goto..

That is, wait on the screen to get a variable entered by the user. I know I can use CHOOSE, but it's an external command. I'd like to know what other methods there are to achieve the function above.

No one answering?

set /p confrim=yes or no?(y/n):
if %confirm% == y goto ..
if %confirm% == n goto..

This can do it, but there is one problem: if the user enters some other character, then %confirm% is neither equal to Y nor equal to n. So add another bit of code:

:re
set /p confrim=yes or no?(y/n):
if /i %confirm% == y goto ..
if /i %confirm% == n goto..

if /i %confirm% neq y goto :re
if /i %confirm% neq n goto :re