my @fields = qw(
       ...
       c_...
       c_...
       c_...
       ...
    );

    foreach (@fields) 
    {    
        $in{$_} = $query->param($_);    

        if (/^c_/ && defined($in{$_})) {
           $check{$_} = "CHECKED";
        }

        ...
    }