Also, I can pretty much predict that your program does not say:
use strict;
use warnings;

Because if it did, you would be getting this:
Can't use string ("0") as a HASH ref while "strict refs" in use ...

In your original post, there are many key details missing:   you said that you did an “upgrade,” but not from what to what.   The code you provided, as noted, probably would not have worked anyway.   Details are absolutely everything.