Coding RECFM=F over RECFM=FB

Give example of Inspect TALLYING / BEFORE INTIAL / AFTER INITIAL. In which situation will use this in COBOL?

01 my_string pic x(30) value 'mainframeinterviews'.we can have operations on the string like inspect my_string tallying tally_ct for all e before intial s and after intial i.inspect my_string replacing all e by r before intal s and after intial