sub Bin2Hex{
              my %truth_table = ( 
               '0000' => '0' , 
               '0001' => '1' , 
               '0010' => '2' , 
               '0011' => '3' , 
               '0100' => '4' , 
               '0101' => '5' , 
               '0110' => '6' , 
               '0111' => '7' , 
               '1000' => '8' , 
               '1001' => '9' , 
               '1010' => 'A' , 
               '1011' => 'B' , 
               '1100' => 'C' , 
               '1101' => 'D' , 
               '1110' => 'E' , 
               '1111' => 'F' , 
                                );
              
              my $count = 0;
              my $hex_string = ''; 
              my $len = $#_ ; 
              #print "len $len" ;
              my $nibble = '' ; 
              my $abit ; 
              my $hex_len ;
               my $hex_nibble ;
              $hex_len = ceil($len/4)  ;    
              #print "hex len $hex_len \n" ; 
              for(my $i=0; $i < $hex_len ; $i++) {
                     for(my $j= 0 ; $j < 4; $j++){
                              $abit = pop(@_) ;
                              if (defined $abit) {
                                       $nibble = $abit.$nibble;  
                              }
                              else {
                                       $nibble = '0'.$nibble ;

                              }
                     }
                      $hex_nibble = $truth_table{$nibble} ; 
                      $hex_string = $hex_nibble.$hex_string ;     
                      $nibble = '' ;
              }
              #print "the converted hex : $hex_string" ;
              return $hex_string ;
 }