#!/usr/bin/perl -w
use strict;

my $input = 0xEF;
my $andMask = (2**(MSbit($input)+1))-1;

printf ("%X\n", ($input<<1) & $andMask);
## prints DE

sub MSbit  ##returns power of 2 of MS bit
{
   my $num = shift;
   my $bit =-1;
   while ($num != 0)
   {
      $num = $num >> 1;
      $bit++;
   }
   return $bit;
}