perl中的$a和$b介绍

即使打开了strict和warnings选项也无妨，下面代码并无错误和警告。
代码如下:
#!/usr/bin/perl
use strict;
use warnings;
sub test {
    $a = 1;
    $b = 2;
    print $a, "/n";
    print $b, "/n";
}
test();
1;


下面是perl文档中对这两个变量的解释：

perldoc perlvar
$a
$b Special package variables when using sort(), see "sort" in perlfunc. 
Because of this specialness $a and $b don't need to be declared (using use vars, or our()) even when using the "strict 'vars'" pragma.  Don't lexicalize them with "my $a" or "my $b" if you want to be able to use them in the sort() comparison block or function.