Hm? Unless I'm missing something, that leaves out the part that's relevant to this thread of how to best code the case fall-through thing in Perl.

If the input is not a multiple of 12 bytes, it needs to do this (from the original C version):

   switch(len)              /* all the case statements fall through */
   {
   case 11: c+=((ub4)k[10]<<24);
   case 10: c+=((ub4)k[9]<<16);
   case 9 : c+=((ub4)k[8]<<8);
      /* the first byte of c is reserved for the length */
   case 8 : b+=((ub4)k[7]<<24);
   case 7 : b+=((ub4)k[6]<<16);
   case 6 : b+=((ub4)k[5]<<8);
   case 5 : b+=k[4];
   case 4 : a+=((ub4)k[3]<<24);
   case 3 : a+=((ub4)k[2]<<16);
   case 2 : a+=((ub4)k[1]<<8);
   case 1 : a+=k[0];
     /* case 0: nothing left to add */
   }
   mix(a,b,c);
[download]

And you left out the $c += $length (using 32-bit integer overflow).

Hmm again... or is the . (chr(0)x11), $p, 12 taking the place of that, to fill out the last "gulp"?

So even if that's not quite right, your answer to how to write such a switch statement is "don't. a more natural way (at a higher level in the algorithm) in Perl suggests itself and prevents the need".

Back to the other thread: thanks for sharing fastest implementation of the mix() function you found in pure Perl.