As I understand ir, using the 'i' modifier in Perl slows down the regexp code. You might benchmark using /YES/ || /yes/ instead.

You appear to be using the s operator to remove any spaces. My guess is that you can replace that with tr/ //d instead, and get a speed improvement.

Finally, it looks like the two blocks of code are identical. Can you instead check for (NO and $value not zero) or YES? to do that block of code?