opendir DIR, "the/base/directory" or die $!;
my @dirs = readdir DIR;
closedir DIR;
shift @dirs; # remove ..
shift @dirs; # and .
@dirs = sort @dirs;
my $highest = $dirs[-1];
$highest =~ s/\D//g;
$highest += 1000;
my $limit = $highest + 10000;
while ($highest < $limit) {
   mkdir "object$highest";
   $highest += 1000;
}