my $prefix = "$to_dir/$base_name";
my $suffix = ".jpg";
my @names = "$prefix$suffix";
for (my $i = 0; $i < 10; $i++ ) {
  push @names, "$prefix.$i$suffix";
  last unless -e $names[-1];
}
while (@names >= 2) {
  rename_and_log($names[-2], $names[-1]);
  pop @names;
}