Use of uninitialized value in addition (+) at a18.pl line 27.
Use of uninitialized value in addition (+) at a18.pl line 27.
Use of uninitialized value in subtraction (-) at a18.pl line 28.
Use of uninitialized value in subtraction (-) at a18.pl line 28.
Use of uninitialized value in division (/) at a18.pl line 29.
Use of uninitialized value in division (/) at a18.pl line 29.
Illegal division by zero at a18.pl line 29.