#!/usr/bin/perl

use strict;
use warnings;

my @STARTPOS = ();
my @ENDPOS = ();
my $str =   "BaaaaBBBBBBaaaaaaaBBBBBBBBBBBBBBBBBBBBaaaBBBBBBBBBBBxB";
print "$str\n\n";

my $i = 0;
while (($i = index($str, 'B', $i)) >= 0)
{
  push(@STARTPOS, $i++);
  while (vec($str, $i++, 8) == 66) {}
  push(@ENDPOS, $i-1);
}


# Display results:
for (my $i = 0; $i < @STARTPOS; $i++)
{
  print "\nstart: ", $STARTPOS[$i], "\t->  end: ", $ENDPOS[$i];
}