#!/usr/bin/perl
use strict;
use warnings;

package Ovl;

use overload '""' => \&mystring;

sub new {
  my $ret = bless {}, shift();
  
  $ret->{_name}     = shift;
  $ret->{_str_code} = \&_str_default;
  
  return $ret;
}
      
sub _str_default { my $self = shift; "!" . $self->{_name} . "!" }

sub mystring {
  my $self = shift;
  
  my $str_code = $self->{_str_code} || \&_str_default;
  
  $self->$str_code( @_ );
}

package main;

my $o = Ovl->new( "default" );

print "$o\n";

my $o_undef = Ovl->new( undef );
$o_undef->{_str_code} = sub { "I R UNDEFINED" };

print "$o_undef\n" if $o_undef;

my $o_numeric = Ovl->new( 15 );
$o_numeric->{_str_code} = sub { sprintf( "%0.5f", shift->{_name} ) };

print "$o_numeric\n" if int( $o_numeric ) == 15;

exit 0;

__END__