The only way that you can predict the order is to build the hash, look at the order of the keys, and then expect that, if you continue using the exact same version of perl on the same hardware and building the hash in the same order, then the order of the keys will probably be the same in the future. This isn't terribly useful, though, since it doesn't allow you to control the order, even without the issue that the order is likely to change about 5 minutes after you start depending on it, if not sooner.

Personally, if I wanted to be able to retrieve from a hash in insertion order, I'd probably build a parallel array and push each new key onto it as it's inserted into the hash. Then I could use the hash itself for random access and look up the appropriate hash keys in the array for insertion-ordered access.

In reply to Re: about order in hash keys by dsheroh
in thread about order in hash keys by spx2

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.