如何使用散列作为Perl子例程的参数？

%first_hash = gen_first_hash();
%second_hash = gen_second_hash();
do_stuff_with_hashes(%first_hash,%second_hash);

sub do_stuff_with_hashes
{
    my %first_hash = shift;
    my %second_hash = shift;

    # do stuff with the hashes
}

我收到以下错误：

Odd number of elements in hash assignment at ./gen.pl line 85.
Odd number of elements in hash assignment at ./gen.pl line 86.
Use of uninitialized value in concatenation (.) or String at ./gen.pl line 124.
Use of uninitialized value in concatenation (.) or String at ./gen.pl line 143.

第85行和第86行是子程序中的前两行，124和143是我访问哈希的位置。当我查看这些错误时，似乎表明我的哈希值未初始化。但是，我可以验证散列值是否具有值。为什么我得到这些错误？