use strict;
use warnings;

package ConfigPack;
our $config = {
    db     => 'postgres',
    prefix => 'PFX_',
};

package SillyPack;
foreach my $config qw(db prefix) {
    no strict 'refs';
    ${$config} = $ConfigPack::config->{$config};
}

package MyMainPack;
foreach my $c (keys %{ $ConfigPack::config }) {
    no strict 'refs';
    printf "%-8s => %s\n", $c, ${"SillyPack::$c"};
}

##</code><code>##

db       => postgres
prefix   => PFX_