Another go, seeing that my previous attempt didn't do what you wanted. I don't see anyone else trying this algorithm, but it may have been done by someone who can write better Perl than I can. 
use strict;
use warnings;

my $nRepeats = 2;
my @sSet = qw (a b c d e f);
my $nLength = 12;

my %sSets;
for my $nKey (0..((@sSet) ** $nRepeats - 1)) {
    my $sKey = "";
    for (1..$nRepeats) {
        $sKey .= $sSet[($nKey / (($#sSet + 1) ** ($_ - 1))) % ($#sSet 
++ 1)];
    }
    $sSets{$sKey} = [@sSet];
}

for (0..$#sSet) {
    splice(@{$sSets{$sSet[$_] x $nRepeats}}, $_, 1);
}

my $sString;
my @sChr;
for (1..$nRepeats) {
    my $sRnd = $sSet[int(rand(@sSet))];
    $sString .= $sRnd;
    push(@sChr, $sRnd);
}

for ($nRepeats + 1 .. $nLength) {
    my $sKey;
    for (@sChr) {
        $sKey .= $_;
    }
    my $sRnd = @{$sSets{$sKey}}[int(rand(@{$sSets{$sKey}}))];
    $sString .= $sRnd;
    push(@sChr, $sRnd);
    shift(@sChr);
}

print "$sString \n";

[download]
The algorithm was developed on one of the hot nights when you couldn't sleep, either. The Perl has taken me 2 days to write with all the other distractions life affords. I learned some useful stuff writing it (thanks, Tye, for helping me in CB), so I'm putting it up even though you have your solution!

Regards,

John Davies

In reply to Re: Random data generation. by davies
in thread Random data generation. by BrowserUk

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