package MyClass;

use base qw(Class::Accessor);

sub set {
    my ($self, $field, $value) = @_;
    my %VALID = (
        fname => qr/^[\w-]+$/,
    );
    if (defined $VALID{$field}) {
        if (ref $VALID{$field} eq 'Regexp') {
            if ($value =~ $VALID{$field}) {
                $self->{$field} = $value;
            } else {
                die "Invalid value '$value'\n";
            }
        } else {
            die "Unknown VALIDATOR";
        }
    }
}
__PACKAGE__->mk_accessors(qw(fname));