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Object/Nil.pm #
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package Object::Nil;
use strict;
use warnings;
use overload
    '0+' => sub { 0 },
    '""' => sub { '' },
    'eq' => sub { ref $_[1] && $_[1]->isa(__PACKAGE__) },
    '==' => sub { ref $_[1] && $_[1]->isa(__PACKAGE__) },
    'ne' => sub { not $_[0] eq $_[1] },
    '!=' => sub { not $_[0] == $_[1] },
    fallback => 1;
 
our $Instance;
 
sub new {
    $Instance = bless { }, shift unless defined $Instance;
    $Instance;
}
 
1;
 
__END__
 
=head1 NAME
 
Object::Nil - The nil object
 
=head1 SYNOPSIS
 
  use Object::Nil;
  my $nil = Object::Nil->new;
  "$nil";     # => ''
  $nil eq ''; # => undef
 
=head1 DESCRIPTION
 
This module provides the nil object which evaluats to an empty string
in string context and 0 in numeric context, but returns false when
compared with them.
 
=head1 COPYRIGHT
 
Unpokopo
 
=cut