It sounds strange that you are using a digest as a regex. Are you sure you don't really want to test for equality?

if ($cache_ref->{Index}[$i] eq $fromto_digest || ref->{Index}[$i] eq $
+tofrom_digest)
{
    $cache_index=$1;
    $index_match=1;
    last;
}
[download]

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