I solved this issue with checking params:
for (@{$c->all_tld}) {
push @$checked, $_ if defined $c->param($_);
}
Or you can delete from params all static options and all remaining params will be checkboxes:
$a = $c->param('A');
delete $c->param('A');
...
@checkboxes = @{$c-params->param}; #Not sure for this line. Forget how to show all options
http://mojolicio.us/perldoc/Mojolicious/Controller#param
For only POST parameters(on bottom of section):
$c->req->body_params