Win8 Strawberry 5.8.9.5 (32)  Tue 10/13/2020 15:55:21
C:\@Work\Perl\monks\pragovnj
>cat junque.txt
foo bar CAST(CAST(hs_date AS DATE FORMAT 'YYYYMMDD') AS CHAR(08)) as hs_date biz boz

C:\@Work\Perl\monks\pragovnj
>perl -p -i.bak -e "s/\QCAST(CAST(hs_date AS DATE FORMAT 'YYYYMMDD') AS CHAR(08)) as hs_date\E/FORMAT_DATE(hs_date, 'YYYYMMDD') as hs_date/g;" junque.txt

C:\@Work\Perl\monks\pragovnj
>cat junque.txt
foo bar FORMAT_DATE(hs_date, 'YYYYMMDD') as hs_date biz boz

C:\@Work\Perl\monks\pragovnj
>cat junque.txt.bak
foo bar CAST(CAST(hs_date AS DATE FORMAT 'YYYYMMDD') AS CHAR(08)) as hs_date biz boz