note ELISHEVA <p>If you want a list of all two letter patterns that appear at least twice somewhere in your string, you need to make three changes to your regex.</p> <ol> <li>you need to make <c>(\w{2,})</c> non-greedy by adding a "?" to the end, e.g. <c>(\w{2,}?)</c>.</li> <li>you need to wrap what comes after <c>(\w{2,}?)</c> with a zero width lookahead group. Otherwise you will miss all the matches between the first and second occurrence of "ab"</li> <li>you need to handle repetitions of your regex slightly differently. Instead of <c>/( mumblefoo )+/</c> you need <c>/mumblefoo/g</c>. Using a + the way you did will only get you the last match found because each time the + causes the regex to repeat, it replaces the previous match.</li> </ol> <p>Taken together these changes will make your regex will look like this: <c>/(\w{2,}?)(?=.*?\1)/g</c>:</p> <code> print $x = "abcdefgxxabcdefgzzabcdsjfhkdfab", "\n"; print "<" . join('|',$x =~ /(\w{2,}?)(?=.*?\1)/g) , ">\n"; #outputs: <ab|cd|ef|ab|cd|ab> </code> <p>You can more info on zerolength lookaheads via [http://perldoc.perl.org/perlre.html#Extended-Patterns|the Extended Patterns section of the perlre manpage on perldoc]</p> 998200 998200