@words = (
           'ab',
           'aabb',
           'aaabbb',
           'aaabbab',
           'xxyy',
           'xxxyyy'
         );
%banks = (
           'ab' => []
         );
ab -> ab
aabb -> ab
aaabbb -> ab
aaabbab -> abab
xxyy -> xy
xxxyyy -> xy
ab aabb aaabbb