C 7654 3210
  1110 1111 =  0xEF = decimal 239

1 1101 1110 left shift one showing carry

  1101 1110 result without carry = 0xDE = 222

##</code><code>##

#!/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;
}

##</code><code>##

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

my $input = 0xEF; #this is 239 in decimal
my $mask = 0xFF;

printf ("%X\n", $input<<1 & $mask);
# prints DE which means 222 in decimal

##</code><code>##

printf ("%X\n", 0xEF<<1 & 0xFF);
# prints DE which means 222 in decimal