Might be a bit faster if you throw out the hash and use an array. BTW, I think one of BrowserUK's later posts added back the originally missing low byte of $c so the check for $len > 7 can go, too.

while ($len--) {
    $H[int($len/4)] += $k[$len] << (8 * ($len % 4));
}
[download]

---
print map { my ($m)=1<<hex($_)&11?' ':'';
$m.=substr('AHJPacehklnorstu',hex($_),1) }
split //,'2fde0abe76c36c914586c';
[download]