Trouble is, either of those cause copying of the referenced substring. Effectively just giving you a reference to an anonymous scalar that is a copy of the substring. You might just as well do: 

my $substr = substr $bigstring, $start, $length;
func( \$substr );

[download]

The purpose of taking a substr ref was to avoid copying large chunks of large string, and allow the large string to be modified in place via that reference.

That said. It seems that taking an (lvalue) substr ref also also triggers copying these days. Albeit with attached magic that means that changes made to the copy also get applied to the original substring. Which is a bit cockeyed.

It never used to, but obviously has for some time--at least since 5.8.6. I'm surprised that I've never noticed it before now. It kind of devalues the purpose of taking a reference to a substring. Methinks whomever made the change did not really get Lvalue refs.

I feel the need to write some XS to (again), give me the ability to to pass a reference to a substring around with causing that substring to be copied.

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
"Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."

In reply to Re^2: Access via substr refs 2000 times slower by BrowserUk
in thread Access via substr refs 2000 times slower by BrowserUk

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.