DiveVal(\%hash, map \$_, @elts) = $val;

##</code><code>##

$hash{ $elts[0] }{ $elts[1] }...{ $elts[n-1] } = $val;

##</code><code>##

foo.bar=val
foo.bar.baz=val

##</code><code>##

$hash{$new_key} = delete $hash{$old_key};

##</code><code>##

$hash{$new_key} = delete $hash{$old_key}
   if exists $hash{$old_key};