i imagine this feature could be used like this:

my $perm = Permutation->new(\@data);
my $count = $perm->cardinality;
my $batches = 10;
my $batch_num = 3;
my $start = $count / $batches * $batch_num;
$perm->state($start);
$perm->run;
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but these numbers can get large enough to require bigints. and bigints are slow enough to noticeably impact performance.