$ perl -le'
my $string = "iiMMMMMMMMMMoooooooooooooooooooooooMMMMMMMMMMiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiMMMMMMMMMMMMMooooooooooooooooooooo";
my $code;

$code .= $1 eq "M" ? $-[0] + 1 . "-$+[0]" : $1 while $string =~ /(.)\1*/g;

print $code;
'
i3-12o36-45i76-88o