If I understand what you want to do correctly, then all you'd need to know is that variables that live in a given package's symbol table (i.e. not those declared with my) are available to other packages as long as their names are fully qualified. So you could give your configuration hash a distinctive name, and put it in the main package, and access it like so:

$main::_my_configuration_hash{$foo}
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I also tentatively suggest you check out the autouse pragma (perldoc autouse) to see if that might be appropriate. It postpones the loading of modules until they're actually used.