If you'll put your results in an array instead of a bunch of scalars, you can avoid dealing with symbolic references in that. That also makes the sort easy.

That may not be useful. You'd probably want some record of the original string, and that's probably what you really want to sort. Put the numbers into a hash with the strings as keys.

my %code = map {
    $_ => calculation($_)
} @strings;
@strings = sort { $code{$b} <=> $code{$a} } keys %code;
[download]