How very odd!

My testing on Win2k, ActivePerl 5.8.8 shows that the case of the data doesn't affect the timing, and that old_way is consistently just shy of 50% faster than with_tr. 

Upper case data
===============
            Rate with_tr old_way
with_tr 183850/s      --    -32%
old_way 272269/s     48%      --

Lower case data
===============
            Rate with_tr old_way
with_tr 182262/s      --    -33%
old_way 270854/s     49%      --

[download]

Benchmark code:

<Reveal this spoiler or all spoilers in this node or all in this thread>

Of course, inlining the code saves a lot of time: 

              Rate   with_tr   old_way with_tr_i old_way_i
with_tr   180473/s        --      -32%      -39%      -52%
old_way   265506/s       47%        --      -10%      -29%
with_tr_i 296058/s       64%       12%        --      -20%
old_way_i 372377/s      106%       40%       26%        --

[download]

Benchmark code:

<Reveal this spoiler>

In reply to Re: Premature and micro optimization... by ikegami
in thread Premature and micro optimization... by chargrill

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.