With the regexp that you posted: 

'<a /><b >' =~ /<([\w\d]+)\s+(?{ print $^N })\s*?>/;
__END__
ab

[download]
The reason is that when the engine first gets to the print statement, the match is still succeeding, so the print proceeds; but, the first match eventually fails, because of the /, so the engine starts searching again, and finds (and prints) the second match. I'm not sure if this answers your question, but at least it illustrates what appears like an iteration.

BTW, \w implies \d, so [\w\d] is redundant.

Update: Also, if in the regexp in Obfuscated regexp you get rid of the \1 at the very end, then the print statements get executed only once. Clearly this \1 is what causes the successive matches to fail, thus forcing the engine to start searching again. Once it is removed, the match succeeds, and the engine stops.

the lowliest monk

In reply to Re: Global Regex sans //g by tlm
in thread Global Regex sans //g by eibwen

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.