1. 当@a被回收时，values的refcount都会减1。
2. 当匿名数组/哈希的refcount为0时，将被回收，同时递归进行步骤1

所以：

@a = ({1,2,3}, [1,2,3]);

当@a被回收时，{1,2,3}和[1,2,3]的refcount都将变为0，从而将被回收。

可以通过对象的destructor来验证这一点：

perl -e'
   {
       package X ;
          sub new { my ($c,$n) = @_; bless(\$n, $c) }
          DESTROY { print ${$_[0]},"\n"; }

       {
          my @a = (
         { a => X->new(1), b => X->new(2) },
         [ X->new(3), X->new(4) ],
          );
          print "Before end of scope\n";
       }
       print "After end of scope\n";
   }
'

输出是：

Before end of scope
4
3
2
1
After end of scope

要特别注意的是对于%hash只会对其values进行refcount减1(当把引用用作key时，会被转为字符串，同时立马refcount减1):

perl -e'
   {
       package X ;
          sub new { my ($c,$n) = @_; bless(\$n, $c) }
          DESTROY { print ${$_[0]},"\n"; }

       {
          my @a = (
         { X->new(1), X->new(2) },
         [ X->new(3), X->new(4) ],
          );
          print "Before end of scope\n";
       }
       print "After end of scope\n";
   }
'

输出：

1
Before end of scope
4
3
2
After end of scope