package Foo::Bar::Baz;

use vars '$quux';
print "What should \$quux hold?\n: ";
chomp( $quux = <STDIN> );

package main;

use strict;

my $hash = \%main::;
for my $key (qw( Foo Bar Baz ))
{
    $hash = $hash->{ $key . '::' };
}

print "Quux is: ${ $hash->{quux} }\n";