my $string = <>;
$string =~ /(\w*(\w)\w*\2\w*)/;
# The beginning of the word, then a notable letter, 
# maybe some middle letters, then that same notable letter as before, 
# then the rest of the word.
print "Found word '$1', with duplicated letter '$2'\n";


##</code><code>##

>image imagination dream
Found word 'imagination', with duplicated letter 'n'
>