Posted just to see if it's what you are looking for, since it seems a little unclear (see other replies :)

perl -ne '/^(?!.*(.)\1)(?=.*(.).+\2)(?=.*(?!\2)(.).+\3)\w{12}$/ and pr
+int' /usr/share/dict/words
[download]

This finds 2657 entries in my 'words' file with no adjacent duplicates but at least two different duplicated letters.