That doesn't seem to yield any output that I can understand. Why three 'b1' 'b2' 'b3' from ab1b2b3b4d and nothing from any of the others? 

c:\@Work\Perl\monks>perl -e
"use warnings;
 use strict;
 use feature qw{ say };
 ;;
 for my $string (qw(ab1b2b3b4d  ab5b6b7d  ab8b9d  abxd  ad)) {
   my @two;
   my @matches = $string =~ /(a)
                             (b.(?{ push @two, $2 if defined $2 }))+
                             (d)/x;
   say for @matches, '---', @two, '======';
   }
"
a
b4
d
---
b1
b2
b3
======
a
b7
d
---
======
a
b9
d
---
======
a
bx
d
---
======
---
======

[download]

Update: "This is perl 5, version 14, subversion 4 (v5.14.4) built for MSWin32-x86-multi-thread"

Give a man a fish:  <%-{-{-{-<

In reply to Re^4: Regex troubles... by AnomalousMonk
in thread Regex troubles... by kepler

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.