It appears that the following regex work differently.
Why \d and [\d] are different?
[A-PR-UWYZ]\d{1,2} and [A-PR-UWYZ][\d]{1,2}
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But when you put characters into brackets, you are telling regex to search for each character represented in the bracket. So [\d] is looking for any single character that is either a \ or a d character. Outside of brackets, regex evaluates \d as any digit.
