Nice JAPH, after I saw the code I started to play with it. I think it's better if you use the -l option. I was bored at wOrk :\

#!perl -l

$a="0"x24;
%b=(x20,[4,C,11],x61,[5,13],x63,[14],x65,[A,E,16],x68,[9,12], x6A,[0],
+x6B,[15],x6C,[10],x6E,[6],x6F,[7],x70,[D],x72,[B,F,17], x73,[2],x74,[
+3,8],x75,[1]);

foreach $c(keys %b){

    foreach(@{$b{$c}}){
        substr $a,hex,1,chr(hex($c));
    }
}

print"$a";
[download]

------------------

#!perl -l

$a="0"x24
;%b=(x20,
[4,C
,11],x61,[5,13],
x63,[14],x65,[A,

E,16],x68,[9,12],
x6A,[0],x6B,[15],
      x6C   ,[10]
,x6E,[6],x6F,[7],
x70,[D],x72,[B,F,

17],x73,[2],x74,[
3,8],x75,[1]);###
    for   $c(keys
    %b){for(@{$b#
    #x70,[D],x72,

{$c}}){substr $a,#
hex,1,chr(hex($c))
      ;}}
print"$a";#fun with
#hashes#x70,[D]x70,
[download]

--------------------

#!perl -l

                        $
                       a=#
                     "0"x24;
                    %b=(x20,[
                   4,C,11],x61
                  ,[5,13],x63,[
                 14],x65,[A,E,16
                ],x68,[9,12],x6A,#
              [0],x6B,[15],x6C,[10]
            ,x6E,[6],x6F,[7],x70,[D],
           x72,[B,F,17],x73,[2],x74,[3
          ,8],x75,[1]);foreach$c(keys%b
         ){foreach(@{$b{$c}}){substr $a,
        hex,1,chr(hex($c));}}print"$a";##
[download]