Hmm. Seems to me that this could be done with a fancy Tie somehow. Not quite as you have posted it though....Perhaps if $m, $o, and $s were also cascaded...
How far would you want this to go? While the above example could be done, I can see it getting messy with subroutine calls. For example:

$n=1; #we have no idea which variables should be cascaded.
$subref=sub { return $n *3 };

print &$subref, "\n";
$n=2;
print &$subref, "\n";
[download]

Will that output
3
6
?.
Stream of conciousness: the Monitor package uses a tie on a variable to track when a variable is changed...can we track when it is accessed, and turn on cascading for any lvalue, etc? (I see dire consequences on the stack/heap, but...) Then when any such value is modified, you could go through the cascade stack and reset every value. It would go nuts on code like:

use Cascade;

cascade $n;
cascade $m;
$n=1;

$m=$n;
$n=$m+1;
[download]

Because $m is altered by $n, and thus when we change $n, we recalc $m, which is in turn set by $n, so we recalc....

But I guess this isn't much different from screwing your reference count by doing a $a=\$a (except of course that that doesn't hang).

All speculation anyway, since I don't believe that there is any way to find what lvalue is affected by a variable reference.