#! perl -slw
use strict;
use constant {
    KEYLEN => 8,
    ALPHA => [ 'A'..'Z' ],
    CONDITION_FREQUENCY => 0.2,
    LIST_SIZE => 1e6,
};

our $MAX ||= LIST_SIZE;

sub rndStr{ join'', @_[ map{ rand @_ } 1 .. shift ] }
sub property { rndStr( KEYLEN, @{+ALPHA} ) }
sub condition_is_true{ rand() < CONDITION_FREQUENCY ? '1' : '0' }

my %records;
foreach my $item ( 1 .. $MAX ) {
    my $key = property($item);
    my( $count, $flag ) = unpack 'Nc', $records{ $key }||pack('Nc', 0, 0 );
    ++$count;
    $flag = 1 if condition_is_true( $item );
    $records{ $key } = pack 'Nc', $count, $flag;
}

printf 'check Memory: '; <STDIN>;

__END__
----------HOHs---------------
my %records;
foreach my $item ( 1 .. $MAX ) {
    my $key = property($item);
    ++$records{ $key }{ count };
    if( condition_is_true( $item ) ) {
        $records{ $key }{ flag } = 1;
    }
}


c:\test>590773 -MAX=1e5
check Memory: 25 MB

c:\test>590773 -MAX=1e6
check Memory: 240 MB

c:\test>590773 -MAX=2e6
check Memory: 480 MB

----------HoAs--------------
use constant { FLAG => 0, COUNT => 1 };

my %records;
foreach my $item ( 1 .. $MAX ) {
    my $key = property($item);
    ++$records{ $key }[COUNT];
    if( condition_is_true( $item ) ) {
        $records{ $key }[FLAG] = 1;
    }
}

c:\test>590773 -MAX=1e5
check Memory: 22 MB

c:\test>590773 -MAX=1e6
check Memory: 210 MB

c:\test>590773 -MAX=2e6
check Memory: 420 MB

--------HoIVs---------
sub sgn{ ($_[ 0 ]||0 ) < 0 ? -1 : 1 }

my %records;
foreach my $item ( 1 .. $MAX ) {
    my $key = property($item);

    $records{ $key } += sgn( $records{ $key } );
    if( condition_is_true( $item ) ) {
        $records{ $key } = - $records{ $key };
    }
}

c:\test>590773 -MAX=1e5
check Memory: 11 MB

c:\test>590773 -MAX=1e6
check Memory: 90 MB

c:\test>590773 -MAX=2e6
check Memory: 180 MB

--------HoPVs(5 bytes)---------
my %records;
foreach my $item ( 1 .. $MAX ) {
    my $key = property($item);
    my( $count, $flag ) = unpack 'nc', $records{ $key }||pack('nc', 0, 0 );
    ++$count;
    $flag = 1 if condition_is_true( $item );
    $records{ $key } = pack 'nc', $count, $flag;
}

c:\test>590773 -MAX=1e5
check Memory: 15 MB

c:\test>590773 -MAX=1e6
check Memory: 120 MB

c:\test>590773 -MAX=2e6
check Memory: 245 MB

--------HoPVs(9 bytes)---------
my %records;
foreach my $item ( 1 .. $MAX ) {
    my $key = property($item);
    my( $count, $flag ) = unpack 'Nc', $records{ $key }||pack('Nc', 0, 0 );
    ++$count;
    $flag = 1 if condition_is_true( $item );
    $records{ $key } = pack 'Nc', $count, $flag;
}

c:\test>590773 -MAX=1e5
check Memory: 15 MB

c:\test>590773 -MAX=1e6
check Memory: 129 MB

c:\test>590773 -MAX=2e6
check Memory: 261 MB