sortby

• Now we have %new_number, which maps the old message numbers to new ones

• Now it's just a matter of renaming files appropriately

 for my $m (keys %new_number) {
 delete $new_number{$m} if $new_number{$m} == $m;
 }

 while (%new_number) {
 my ($cur) = keys %new_number;
 my @chain;
 do {
 push @chain, $cur;
 $cur = delete $new_number{$cur};
 } while $cur != $chain[0];
 print STDERR "Chain: (@chain)\n" if $VERBOSE;

 my ($prev, @rest) = reverse @chain;
 my $TMP = "$prev.TMP";
 rename("$dir/$prev", "$dir/$TMP") or die "$prev => $TMP: $!";
 for my $cur (@rest) {
 rename("$dir/$cur", "$dir/$prev") or die "$cur => $prev: $!";
 $prev = $cur;
 }
 rename("$dir/$TMP", "$dir/$prev") or die "$TMP => $prev: $!";
 }