#!/usr/bin/perl
use strict;
use warnings;

my @M = 'a' .. 'z';
my $N = 42; # Assumes N is > 2

my ($minus_1, $minus_2) = ($M[rand @M], $M[rand @M]);
my $str = $minus_1 . $minus_2;

for (1 .. $N - 2) {
    my $idx = rand @M;
    $idx = ($idx + (int(rand $#M) + 1)) % @M if $minus_1 eq $minus_2 && $M[$idx] eq $minus_2;
    $str .= $M[$idx];
    ($minus_1, $minus_2) = ($minus_2, $M[$idx]);
}
print "$str\n";