This morning I was re-reading require to refresh my memory on an issue unrelated to this question. While reading, I stumbled across something that I hadn't noticed in previous reads:

You can also insert hooks into the import facility, by putting directly Perl code into the @INC array. There are three forms of hooks: subroutine references, array references and blessed objects.

After reading the rest of the document I think I understand that the execution of the coderef held in @INC should return a filehandle to a file that is to be included, and it also looks like the rest of @INC will not be used unless the code returns undef instead of a filehandle.

Of course I've also read the examples given in the POD for require, but I guess I'm just not quite seeing it. perlvar's brief mention of the @INC and %INC hooks didn't really contribute to settling my curiosity. What is this feature for, and how is it correctly used? It seems that it must be used for runtime decisions on what files get included. Am I close to being on the right track? Can anyone provide an example of this feature at work?

Thanks for any comments!

UPDATE: I found the first mention of the @INC coderef feature in perl573delta, with the following line (in the Changes section: "21. document the coderef-in-@INC feature." That implies it's been around since before 5.7.3, but first documented in 5.7.3.


Dave

In reply to How to use @INC coderef hooks by davido

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.