#!/usr/bin/env perl
use strict; use warnings; use feature qw/say/;

package Foo;
our $foovar; BEGIN{ $foovar = 42 }

package main;

# This does not work (gets "Variable $mainvar is not imported")
BEGIN{ package main;   *main::mainvar = \$Foo::foovar; }

# But this does work ... why?
#BEGIN{ package xyzzx;  *main::mainvar = \$Foo::foovar; }

say $mainvar;