my $validate = create_dptable Validate;
my %params; # store params in a hash.  Use symrefs to obtain original behaivor.
            # (i.e. $$_ = ...)

foreach (params()) {
    $params{$_} = exists $validate->{"val_$_")
                ? $validate->{"val_$_"}->(param($_)) 
                : $validate->{'error_page'}->($_)
}