BEGIN {
  %main::_shared_vars = (
    the_very_global => \$the_very_global
  );
}
INIT {
  package main;
  sub _iterate_packages_loop {
    my($stash,$name,$callback) = @_;
    $callback->($stash,$name);
    foreach (keys %{$stash}) {
      if (/::\z/ and $_ ne "main::") {
      _iterate_packages_loop($stash->{$_},$name.$_,$callback);
      }
    }
  };
  sub _iterate_packages {
    _iterate_packages_loop(\%::,"main::",shift);
  }
  _iterate_packages(sub { 
    $_[1] eq "main::" and return;
    while (my($k,$v) = each %::_shared_vars) {
      $_[0]->{$k} = $v;
    }
  });
}

$the_very_global = "GLOBAL!\n";

print $the_very_global;

package bar;

print $the_very_global;

package bar::foo;

print $the_very_global;

##</code><code>##

BEGIN {
  %main::_shared_vars = (
    the_very_global => \$the_very_global
  );
}
BEGIN {
  use Filter::Util::Call;
  use strict;
  my $_strict_import = \&strict::import;
  package strict;

  sub _add_to_stash {
    my $name = shift;
    no strict 'refs';
    while (my($k,$v) = each %::_shared_vars) {
      # importing this way makes the variable
      # be considered "declared" for the purposes
      # of strict.
      *{$name."::$k"} = $v;
    }
  };
  *strict::import = sub {
    # setup the package we are being called by
    _add_to_stash(scalar caller);
    filter_add(sub {
      my $status;

      while (($status = filter_read()) > 0) {
        _add_to_stash($1) while /package\s+([\w:]+)/g;
        last unless(/package\s*\z/);
      }
      return $status;
    });
    goto &$_strict_import;
  };
}