Why then did you not bother to write a few lines like: 

use strict;
use warnings;
use Benchmark 'cmpthese';

my $string = map { ('a'..'z')[rand 26] } 1..30;
my @sub_fields;
cmpthese( -1, {
           regex1 => sub { @sub_fields = $string =~ /\w{5}/g },
           regex2 => sub { @sub_fields = $string =~ /.{5}/g },
           unpack => sub { @sub_fields = unpack '(A4)*', $string },
           substr => sub { @sub_fields = map { substr $string, 5*$_, 5
+ } 0..length( $string )/5-1 },
          });

[download]

that already shows that the regex idea is vastly inferior:

             Rate substr unpack regex1 regex2
substr   696486/s     --   -57%   -94%   -94%
unpack  1603093/s   130%     --   -85%   -86%
regex1 10731041/s  1441%   569%     --    -4%
regex2 11165392/s  1503%   596%     4%     --

[download]

In reply to Re^3: Performance problems on splitting long strings by hdb
in thread Performance problems on splitting long strings by Laurent_R

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.