Benchmarked a few solutions:

use Benchmark qw(:all);

my $str = 'iiiiiiiiMMMMMMMMMMMooooooooooooMMMMMMMMMMiiiiiMMMMMMMMoooo'
+;

my $these = {
    'count' => sub {
        my $count = 0;
        $count++ while $str =~ /(M+)/g;
        $count;
    },
    'regex' => sub {
        my $count = () = $str =~ /(M+)/g;
    },
    'split' => sub {
        $#{[split /M+/, $str, -1]};
    },
};

printf "%-10s %d\n", $_, $these->{$_}->() for sort keys %$these;
print "\n";

cmpthese(-1, $these);

[download]

Got these:

count      3
regex      3
split      3

          Rate split regex count
split 335814/s    --   -3%  -30%
regex 345739/s    3%    --  -27%
count 476625/s   42%   38%    --

[download]

In reply to Re: Can you write a faster code to perform this task? by Anonymous Monk
in thread Can you write a faster code to perform this task? by Anonymous Monk

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.