Well, solution for my own problem :-), thanks to reading Re: Defining classes and inheritance using packages within a single .pl file, without creating modules.

It ended up to be a simple thing. I must put my package before the main script, something like:

use strict;

package A;
... # yada yada yada

package main;
...
[download]

so it loads properly, or put my package definitions inside BEGIN blocks. By load properly I mean, mk_accessors is called before objects from A are used, so the accessors are there.