my %query = ( some => "default relevant to controller" );

my @stuff = $c->request->param("some_checkbox_list");

$query{foo} = { in => \@stuff } if @stuff;

$query{something} = "tacos" if $something_taco_related;

# a dozen more similar style, disparate variable loads.

my %where = ( some => "dynamic",  list => "of conditions" );

my $rs = $c->model("DBIC::SomeTable")
    ->search(\%query, { join => [ blah, blah ], %where });
$c->stash( some_stuff_rs => $rs );