I'm dumping my previous answer in favor of pointing you here. At least until I figure out a concise answer.

Update: Ok, I worked it out:

use strict;
use warnings;

package foo;
our $var = 'got it';

package main;
my $pkg = 'foo';
my $v = 'var';
print ${$main::{$pkg.'::'}{$v}};
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Note that you get no hassles about symbolic references. "main::" is the name of the hash that includes the symbol tables for all the other packages. You index it by the package name (with double-colon appended), and then the variable name. That gives you a glob reference, which you can dereference using the appropriate sigil.