As with most performance questions the best way to find out is to Benchmark it: 

use Benchmark qw(cmpthese);

cmpthese(-5, { NoPlus => sub { $_ = 'a' . ('x' x 1000) . 'b'; s/x//g }
+,
               Plus   => sub { $_ = 'a' . ('x' x 1000) . 'b'; s/x+//g 
+} });

[download]

Produces these results: 

$ perl subs.pl
           Rate NoPlus   Plus
NoPlus   2674/s     --   -98%
Plus   115762/s  4230%     --

[download]

So it would appear that using + for your iteration is 42 times faster than using s///g! Of course the exact difference will depend on the string being matched. When I changed the number of x's to 100 the difference dropped to 12 times. When I changed it to produce a string of 'axaxax...' there was almost no difference between the two solutions.

-sam

In reply to Re: regex internals: quantifiers vs global match by samtregar
in thread regex internals: quantifiers vs global match by davidrw

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.