#!/usr/local/bin/perl -w
use strict;

my @words = qw/ beriberi
    coco
    couscous
    deed
    toot
    toto
    tutu
    assa
    ssaa
    /;

for (@words) {
    print "$_\n" if /^(\w+)\1$/ || /^(\w+)(\w+)\2\1$/;
}

##</code><code>##

beriberi
coco
couscous
deed
toot
toto
tutu
assa