in reply to Re^2: Noob Question - not sure what's wrong
in thread Noob Question - not sure what's wrong

That matches "SB00\n" and you said it shouldn't. Replace /$/ with /\z/ to get the stated desired behaviour.

\d can match more than 0-9. I presume you don't want to match arab digits.

That uses needless captures. Get rid of them.

m/^(SB)(\d{1,2})$/i
should be
m/^SB[0-9]{1,2}\z/i