Hello, QM,

Haven't heard about such capture groups for only backreferences.
Interestingly, if any simple overcome exist? This overcome below looks ugly: 
#!/usr/bin/perl -wl

print map "[$_]", "bogus firstblahj?keblahthird bogus" =~ /
    (?| (*F)
        | first ( (blah) .*? \2 ) third (?{ $L = $1 }) (*THEN) (*F)
        #       1 2    2        1
        | (??{ defined $L ? "" : "(*F)" })
          (first) (??{ print "mid-match:[$L]" ; quotemeta $L }) (third
+)
        # 1     1                                               2     
+2
        )
    /x;

[download]
output: 
mid-match:[blahj?keblah]
[first][third]

[download]
Idea here is to use conditional '(?|...)' with 2 groups, save mid-match (if full match is successful), fail first branch anyway, then match same thing on alternative branch rewriting $1 and $2, and using previously defined mid-match to avoid captures.

In reply to Re: Regex backreference without capture by rsFalse
in thread Regex backreference without capture by QM

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.