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

package UglyTie;
use Data::Dumper;

sub TIESCALAR {
    my $class = shift;
    bless [ @_ ], $class;
}

sub STORE {
    warn Dumper @_;
}

sub FETCH {
    warn Dumper @_;
    1;
}
package SillyClass;

sub new {
	bless \$_[ 1 ], $_[ 0 ];
}

sub modifySubstring: lvalue {
	my( $self, $start, $length ) = @_;
	substr( $$self, $start, $length );

      ## Validate that part of the string that was modified
	# die 'Bad value' 
	#	unless substr( $$self, $start, $length ) =~ m[^[a-z]+$];
}

1;

package main;

my $silly = SillyClass->new( 'a teststring' );
$silly->modifySubstring( 3, 3 ) = 'ABC';