my @types = qw(
  date
  integer
  text
  timestamp
);

foreach my $type (@types) {
    my $function = uc $type;
    no strict 'refs';
    *$function = sub {
        if ( looks_like_number( $_[0] ) ) {
            die "Datatype '$type' does not require a numeric length '$_[0]'";
        }
        return { type => $type, @_ };
    };
}