use Math::Random::MT;
my $mt = Math::Random::MT->new();
sub badRand($) { rand() < 0.5 ? 0 : rand( $_[0] ) }
sub goodRand($) { rand($_[0]) }
sub bestRand($) { $mt->rand($_[0]) }
##</code><code>##

#!/usr/bin/env perl

use strict;
use Statistics::ChiSquare;
use Math::Random::MT;

my $mt = Math::Random::MT->new();

my $NUMTESTS = 100000;

sub badRand($) { rand() < 0.5 ? 0 : rand( $_[0] ) }
sub goodRand($) { rand($_[0]) }
sub bestRand($) { $mt->rand($_[0]) }

my %tests = (
        'bad_shuffle' => {
                'randsub' => \&badRand,
                'rands' => undef
        },
        'good_shuffle' => {
                'randsub' => \&goodRand,
                'rands' => undef
        },
        'best_shuffle' => {
                'randsub' => \&bestRand,
                'rands' => undef
        },
);
my @vals = ( 1..4 );

foreach (keys %tests){
        my $asub = $tests{$_}->{'randsub'};
        $tests{$_}{'results'} = do_a_shuffle($asub, @vals);
        $tests{$_}{'chi'} =  Statistics::ChiSquare::chisquare(values %{$tests{$_}{'results'}});
        print $_ . " : " . $tests{$_}{'chi'}."\n";
}
# &randsub, @choices
sub     shuffle {
        my $randsub = shift;
        # rest of params are the values/choices to shuffle
        $a = $_ + $randsub->( @_ - $_ ),
        $b = $_[$_],
        $_[$_] = $_[$a],
        $_[$a] = $b
                for 0 .. $#_;
        return @_;
}
# &randsub, @choices
sub     do_a_shuffle {
        my %tests;
        for(1..$NUMTESTS){
                ++$tests{ join '', shuffle(@_) };
        }
        return \%tests;
}
__END__