There are many possibilities for why what happened happened. None are likely to be heavily documented.

If the content method returns a different Perl scalar each time with the same contents, then what happens is that each pattern match is matching a scalar that has never been matched before. So each time Perl will start from the beginning.

If the content method attempts to do a pattern match internally, then pos is being reset.

If it directly assigns to pos (I can't imagine why it would but...), then that assignment wins.

In any case few module authors would think about someone trying to do a pattern match like this, so it is a good idea not to expect it to be documented accurately, and not to rely on them making your life easy. Putting the content into a scalar like graff suggested is a generally good idea unless you really know the code you are calling, and how Perl will deal with that.

In reply to Re: Re: Re: backreference question. by tilly
in thread backreference question. by Qiang

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.