Always start with the earliest error in the code. In this case it is on line 19: 'syntax error at ./BP_Chap11_Exer1.pl line 19, near "$_}"'. Once you fix that issue there are three or four more of a similar nature. Fix those and the elsif issue and you are left with one final issue due to a missing }. Your indentation is mostly pretty good so it should be easy enough to see where the missing } should go.