my %dispatch = (
     11 => sub{ $c+=$k[10]<<24 },
     10 => sub{ $c+=$k[9] <<16 },
     9 =>  sub{ $c+=$k[8] <<8  },
     8 =>  sub{ $b+=$k[7] <<24 },
     7 =>  sub{ $b+=$k[6] <<16 },
     6 =>  sub{ $b+=$k[5] <<8  },
     5 =>  sub{ $b+=$k[4]      },
     4 =>  sub{ $a+=$k[3] <<24 },
     3 =>  sub{ $a+=$k[2] <<16 },
     2 =>  sub{ $a+=$k[1] <<8  },
     1 =>  sub{ $a+=$k[0]      }
);

&{$dispatch{$_}} for reverse 1..$len;