package Tie::Hash::PEach;
use strict;
use warnings;

sub FIRSTKEY {
    my( $self     ) = shift;
    my( %hash     ) = %{ $self->[0] };
    my( $iterator ) = $self->[1]{ITER};
    my( @keys     ) = keys %hash;
    $iterator = 0 unless defined $iterator;
    my( @pair ) = ( $keys[ $iterator ], $hash{ $keys[ $iterator ] } );
    $iterator = ( $iterator < $#keys ) ? $iterator + 1 : undef;
    $self->[1]{ITER} = $iterator;
    @{$self->[1]{KEYS}} = @keys;
    return wantarray ? @pair : $pair[0];
}

sub NEXTKEY {
    my( $self     ) = shift;
    my( %hash     ) = %{ $self->[0] };
    my( $iterator ) = $self->[1]{ITER};
    my( @keys     ) = @{ $self->[1]{KEYS} };
    $iterator = 0 unless defined $iterator;
    my( @pair ) = ( $keys[ $iterator ], $hash{ $keys[ $iterator ] } );
    if ( $iterator < $#keys ) {
        $iterator++;
        $self->[1]{ITER} = $iterator;
        return wantarray ? @pair : $pair[0];
    } else {
        $iterator = undef;
        $self->[1]{ITER} = $iterator;
        return undef;
    }
}

sub TIEHASH { 
    bless [ {}, { ITER => undef, KEYS => [] } ], shift;
}

sub STORE {
    my( $self, $key, $value ) = @_;
    ${$self->[0]}{$key} = $value;
}

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

sub EXISTS {
    my( $self, $key ) = @_;
    return exists ${$self->[0]}{$key};
}

sub DELETE {
    my( $self, $key ) = @_;
    delete ${$self->[0]}{$key};
}

sub CLEAR {
    my $self = shift;
    %{$self->[0]} = ();
}

sub SCALAR {
    my $self = shift;
    scalar %{$self->[0]};
}

1;

package main;

use strict;
use warnings;
use Data::Dumper;

my $obj = tie my %hash, "Tie::Hash::PEach";

%hash = qw/one 1 two 2 three 3 four 4 five 5 six 6/;
print "\n\nThe order of \%hash:\n";
print Dumper \%hash;
{
    print "\n\nLocalized 'each' instance iterator for \%hash:\n";
    # To change 'each' iterator for %hash, set $obj->[1]{ITER}.
    # Remember, the first element is 0.
    local $obj->[1]{ITER} = 2;
    my ( $key, $value ) = each %hash;
    print "$key => $value\n";
}

print "\n\nNonlocalized 'each' instance iterator for \%hash:\n";
my ( $key, $value ) = each %hash;
print "$key => $value\n";