使用Scalar::Util::weaken:

{    
my @data1 = qw(one won);

my @data2 = qw(two too to);

push @data2, \@data1;

push @data1, \@data2;

weaken($data1[2]);

weaken($data2[3]);

}
{
    my $sub = sub {
        print $sub;
    };
    weaken($sub);
    print Dump $sub;
}

另外可用Devel::Cycle::find_cycle查找循环引用