#! perl -slw
use strict;

package Chipper;
my %pos;

sub TIESCALAR {
	my( $class, $string ) = @_;
	my $self = bless \$string, $class;
	$pos{ $self } = 0;
	return $self;
}

sub FETCH { 
	my( $self ) = @_;
	return $$_[ 0 ];
}

sub STORE { 
	my( $self, $value ) = @_;
	$pos{ $self } = 0;
	return $$self = $value;
}

sub chip {
	my( $self ) = @_;
	$pos{ $self } = 0, return undef if $pos{ $self } >= length $$self;
	return substr $$self, $pos{ $self }++, 1;
}

1;

package main;

my $inst1 = tie my $str1, 'Chipper', 
	'The quick brown fox jumps over the lazy dog';
my $inst2 = tie my $str2, 'Chipper', 
	'Now is the time for all good men to come to the aid of the party';

print "($a$b)" while $a = $inst1->chip and $b = $inst2->chip;