# Accessor_Factory.pm
use strict;
use warnings;

package Accessor_Factory;

1;  # appease the wrath of require

sub make_getsets {
  my @fields = @_;
  my $class = caller;
  for my $field ( @fields ) {
    my $code = <<EOCODE;
    {
      package $class;
      use Carp 'carp';
      sub $field : lvalue {
        my \$self = shift;
        carp "Only first argument to method $field of class $class is used"
          if \@_ > 1;
        \$self->{ $field } = shift if \@_;
        \$self->{ $field };
      }
    }
    1;
EOCODE
    eval $code or die $@;
  }
  return;
}
__END__

##</code><code>##

# Foo.pm
use strict;
use warnings;

package Foo;

1;

BEGIN {
  use Accessor_Factory;
  Accessor_Factory::make_getsets( qw( bar baz ) );
}

sub new {
  return bless +{}, shift;
}
__END__

##</code><code>##

# demo.pl
use strict;
use warnings;

use Foo;

my $foo = Foo->new();

$foo->bar = 1;
print $foo->bar, "\n";

$foo->bar += 2;
print $foo->bar, "\n";

$foo->bar( 5 );
print $foo->bar, "\n";

print $foo->baz = 8, "\n";
print $foo->baz *= 11, "\n";
print $foo->baz( 100 ), "\n";

__END__

##</code><code>##

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