((\\)+\1)* is not equivalent to (\\\\)* because of the grouping (and the multiplier, but that part is obvious). I think, because you group the entire term ((\\)+\1)) then \1 is not refering to the (\\). I believe \1 would be undefined at that moment because you are actually inside the first pattern which would be ((\\)+\1)).

I am sure you want to use the ?: operator which "is for clustering, not capturing" which is from the perlre perldoc. Using ?:, the outer group will not get reference to \1 or $1, so the (\\) will get referenced to \1. Then (?:(\\)+\1))* should be equivalent to (\\+\\)*

I am sure this is all vague and confusing to most, but I hope it helped a little.

In reply to RE: RE: Re: Backslashes in regular expressions by perlmonkey
in thread Backslashes in regular expressions by nuance

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.