报价：

@_: Within a subroutine the array @_ contains the parameters passed to that subroutine.

更多细节可以发现在perldoc perlsub (Perl subroutines)链接从perlvar：

Any arguments passed in show up in the
array @_ .

Therefore,if you called a function with two arguments,those
would be stored in $_[0] and $_[1].

The array @_ is a local array,but its
elements are aliases for the actual scalar parameters.
In particular,if
an element $_[0] is updated,the
corresponding argument is updated (or
an error occurs if it is not
updatable).

If an argument is an array or hash element which did not exist when the function was called,that element is created only when (and if) it is modified or a reference to it is taken. (Some earlier versions of Perl created the element whether or not the element was assigned to.) Assigning to the whole array @_ removes that aliasing,and does not update any arguments.