When you have a field with years and qtrs i.e "2021 Q3" and want to only capture the Year and Qtr rows. The regex match used:
^\d{4}\sQ[1234]
Or,
\d{4} Q[1-4]
the ^ is rendundant as you have to match the whole string. [1-4] does a range and saves you a character. and a ' ' instead of \s will match a space instead of any whitespace character (though it does have the disadvantage that it's harder to see sometimes).