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


my @bad_strings = qw(ee);
my @good_strings = qw(ef);

foreach (@bad_strings) {
	print "$_ failed\n" if /(.)(?!\1|$)/;
}
foreach (@good_strings) {
	print "$_ failed\n" if not /(.)(?!\1|$)/;
}