使用严格和使用警告做不同的事情.

从严格模块的手册页：

strict − Perl pragma to restrict unsafe constructs

来自perlrun(for -w)：

prints warnings about dubIoUs constructs,such as variable names that are mentioned only once and scalar variables that are used before being set,redefined subroutines,references to undefined filehandles or filehandles opened read-only that you are attempting to write on,values used as a number that don’t look like numbers,using an array as though it were a scalar,if your subroutines recurse more than 100 deep,and innumerable other things.