package Mytest;
use strict;
use warnings;

my $var = 1;

1;

##</code><code>##

use strict;
use warnings;
use Mytest;

print $Mytest::var . "\n";

##</code><code>##

use strict;
use warnings;
use Mytest;

print $var;

##</code><code>##

use Mytest;
print $var;

##</code><code>##

use Mytest;
print $Mytest::var;

##</code><code>##

#!/usr/bin/perl -w

package Problem;

use strict;
use warnings;
use Scalar::Util qw(refaddr);

{
   my %key1_of;      # leave blank test
   my %key2_of = (); # initialize test
   my %key3_of;
   BEGIN
   {
      %key3_of = (); # initialize with a BEGIN
   }

   sub new
   {
      my ($class, $ar1, $ar2, $ar3) = @_;
      my $new_object = bless \do{my $anon_scalar}, $class;
      $key1_of{refaddr($new_object)} = $ar1;
      $key2_of{refaddr($new_object)} = $ar2;
      $key3_of{refaddr($new_object)} = $ar3;
      return $new_object;
   }

   sub get_key1
   {
      my $self = shift;
      return $key1_of{refaddr($self)};
   }

   sub get_key2
   {
      my $self = shift;
      return $key2_of{refaddr($self)};
   }

   sub get_key3
   {
      my $self = shift;
      return $key3_of{refaddr($self)};
   }

}

1;

# Here's a user of the above object.

package Main;  


use strict;
use warnings;

# Below: Creating values for the sake of showing the issue at hand...

# First variable: assigning undef (declaring its initial value), 
# but due to a subroutine or other complex series of processing, it
# gets assigned a value during a BEGIN block
my $p1 = undef;   # using the 'always assign a value' paradigm here
my $p2;           # leaving it blank for now
my $p3 = undef;   # same 'always assign' paradigm here, but not used in 'begin'

# some processing happens in here; for example, let's say these variables are
# dependent on user input or automatic config files, so $p1, $p2, $p3 might 
# not ever be used.  It just turns out that this time, they all are.

# However, the user of the package creates these instances of the object in a
# begin block, and for whatever reason, the user can't avoid doing this.
BEGIN
{
   $p1 = Problem->new('P11', 'P12', 'P13');
   $p2 = Problem->new('P21', 'P22', 'P23');
}
$p3 = Problem->new('P31', 'P32', 'P33');

sub printit # for display purposes
{
   my $p = shift;
   if (defined $p)
   {
      print "   k1: " . $p->get_key1() . "\n";
      my $k2 = $p->get_key2();
      $k2 = "(undef)" if ! defined $k2;
      print "   k2: $k2\n";
      print "   k3: " . $p->get_key3() . "\n";
   }
   else
   {
      print "   Error: Object is undefined.\n";
   }
};


print "P1:\n";
printit($p1);
print "   (Due to scoping of the undef assignment, the object itself is lost.)\n";
print "P2:\n";
printit($p2);
print "   (Note loss of key 2's value; it's lost because %key2_of\n" .
      "    is assigned to () after the object's creation).\n";
print "P3:\n";
printit($p3);
print "   (As expected, no issues at all).\n";