2. Do both strings contain the same number of M substrings? (In this case yes, because both have 13).

I count 14 for both:

use warnings;
use strict;

my $string1 = "IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
+IIIIIIIIIIIIIMMMMMMMMOOOOOOOOOOOOOOOOOOOOOOOOOOOMMMMMMMMMIIIIMMMMMMMM
+MMMMMOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOMMMMMMMMMIIIMMMMMMMMMMMOOOOOOOOOO
+OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOMMMMMMMMMMMMMIIIIIMMMMM
+MMMMMMOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOMMMMMMMMMIIIMMMMMMMMMOOOOOOO
+OOOOOOOOOOOOOOOOOOOOOOOOOOOMMMMMMMMMMMIIIMMMMMMMMMOOOOOOOOOOOOOOOOOOO
+MMMMMMMMMIIIIIIIIIIIIIIIIIIIIIIIIIIIMMMMMMMMOMMMMMMMMMMMMM";
my $string2 = "IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
+IIIIIIIIIIIIMMMMMMMMMMMMOOOOOOOOOOOOOOOOOMMMMMMMMMMMMMMMMIIIIIMMMMMMM
+MMMMMMOOOOOOOOOOOOOOOOOOOOOOOOMMMMMMMMMMMMMMMIIIMMMMMMMMMMMMMMOOOOOOO
+OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOMMMMMMMMMMMMMMMIIIMMMMMMM
+MMMMMMMMOOOOOOOOOOOOOOOOOOOOOOOOOOOOMMMMMMMMMMMMMMIIIMMMMMMMMMMMMMMMO
+OOOOOOOOOOOOOOOOOOOOOOOOMMMMMMMMMMMMMMIIIMMMMMMMMMMMMOOOOOOOOOOOOOOOM
+MMMMMMMMMIIIIIIMMMMMMMMMMMMOOOOOOOOOOOOOOOOOMMMMMMMMMMMMII";

print mgroups($string1), "\n";
print mgroups($string2), "\n";

sub mgroups {
    my $str = shift;
    my $cnt = 0;
    while ($str =~ /M+/g) {
        $cnt++;
    }
    return $cnt;
}

__END__

14
14
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