As revdiablo has said Readonly is not a core module, whereas constant is a pragma. There are some shortcomings in the use of the constant pragma and all of those are in fact well pointed out in the documentation for Readonly. However Readonly has a performance penalty and there is at least one 'speed up' module ( Readonly::xs ) on CPAN for it and some useful alternatives. One particularly cunning one is Scalar::Readonly which although it works only on scalars allows you to programatically 'write enable' a variable, update it and then lock it again. Of course the variable can be tested as well.

I will very rarely use constant, I have never used Readonly. We do some tricks using Scalar::Readonly ocasionally.

jdtoronto

In reply to Re: What is the difference between the constant construct in Perl and the Readonly construct in Perl? by jdtoronto
in thread What is the difference between the constant construct in Perl and the Readonly construct in Perl? by jira0004

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.