Unquoted string "dev" may clash with future reserved word at ./nelson.pl line 15.
Unquoted string "null" may clash with future reserved word at ./nelson.pl line 15.
...
Argument "dev" isn't numeric in division (/) at ./nelson.pl line 15, <ARGUMENTS> line 1.
Argument "" isn't numeric in division (/) at ./nelson.pl line 15, <ARGUMENTS> line 1.
Illegal division by zero at ./nelson.pl line 15, <ARGUMENTS> line 1.