I am curious about your benchmark program.
With my $str = "\nFoo\n\nBar Quz\nBaz\nx" x 500000;
I get: 
5.020002
            (warning: too few iterations for a reliable count)
            (warning: too few iterations for a reliable count)
            (warning: too few iterations for a reliable count)
      s/iter index regex split
index   26.5    --  -61%  -66%
regex   10.3  158%    --  -12%
split   9.05  193%   13%    --

[download]
which basically means that the results don't matter.

Code as with my $str = "\nFoo\n\nBar Quz\nBaz\nx" x 50000;
Your benchmark default. 

5.020002
            (warning: too few iterations for a reliable count)
            (warning: too few iterations for a reliable count)
        Rate index regex split
index 1.16/s    --  -21%  -34%
regex 1.47/s   27%    --  -16%
split 1.74/s   51%   19%    --

[download]
I am not sure what this means if anything.

In reply to Re: Is foreach split Optimized? by Marshall
in thread Is foreach split Optimized? (Update: No.) by haukex

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.