The reason the code assigns to a variable outside the scope of block is to avoid a smart optimizer optimizing the '&' or '% 2' away, as the result isn't used at all. I didn't want to dive into the Perl source code and see whether '&' or '%' checked their context and decide to do nothing in void context. If one or both would do so, the benchmark would be flawed. It's the same for an assignment to a variable that's about to go out of scope; if the variable doesn't have magic attached, one might not do the assignment after all. I've been bitten by the optimizations Perl makes so many times when benchmarking, I'm very careful and try to give the leave as little room for short cuts as possible. Hence my preference for assigning to a variable whose scope goes beyond the block being tested.

As for your version, Perl parses ++$counter1 & 1 and 1 as '???' if ++$counter1 & 1. I don't know how much that means for the benchmark.

In reply to Re^4: &1 is no faster than %2 when checking for oddness. (Careful what you benchmark) by Anonymous Monk
in thread &1 is no faster than %2 when checking for oddness. Oh well. by diotalevi

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.