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.

  1. you need to make (\w{2,}) non-greedy by adding a "?" to the end, e.g. (\w{2,}?).
  2. you need to wrap what comes after (\w{2,}?) with a zero width lookahead group. Otherwise you will miss all the matches between the first and second occurrence of "ab"
  3. you need to handle repetitions of your regex slightly differently. Instead of /( mumblefoo )+/ you need /mumblefoo/g. 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.

Taken together these changes will make your regex will look like this: /(\w{2,}?)(?=.*?\1)/g:

print $x = "abcdefgxxabcdefgzzabcdsjfhkdfab", "\n";
print  "<" . join('|',$x =~ /(\w{2,}?)(?=.*?\1)/g) , ">\n";

#outputs: <ab|cd|ef|ab|cd|ab>

[download]

You can more info on zerolength lookaheads via the Extended Patterns section of the perlre manpage on perldoc

In reply to Re: RegEx + vs. {1,} by ELISHEVA
in thread RegEx + vs. {1,} by Sewi

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.