Exactly!

It just seems like a logical abstraction that i find it hard to believe that someone hasn't done it before. either that, or i am missing something.

I mean, it seems facile to come up with a very basic DTD which only specified column names and a series of regexps which that column data must match in order to be accepted.

Of course, this only allows 'intra' data checking; there is still the 'inter'-data checking - looking up external databases to see if X has been entered before etc etc...

either way, being able to specify column data semantics in an external file certainly has it's virtues -- it would be such a simple thing to wrap this in an object:

package SyntaxChecker;

our $Column_Definitions = {};    
BEGIN {
    load_definitions();
}

sub new 
{
    my $proto = shift;
    my $column_name = shift || die;
    my $class = ref $proto || $proto;

    my $this = {
        column_name => $column_name,
        column_definition => $class->_get_definition(  
                             $column_name ),
        regexp => [ $class->_get_regexps( $column_name) ],
        regexp_cache => [],
    }; 

    return $this;
}

sub get_cached_regexps
{
    my $this = shift;
    return @{ $this->{'regexp_cache'} };
}

sub validate
{
    my $this = shift;
    my $input_data = shift || die;
    my $matched;

    if ( my @regexps = $this->_get_cached_regexps() ) {
        foreach my $regexp_sub ( @regexps ) {
            $regexp_sub->( $input_data ) ||
                die $this->{'column_definition'};
            $matched++; 
        }
    } else {
        foreach my $regexp ( @{$this->{'regexp'}} ) {
            my $code = eval "sub{ $input_data =~ $regexp }";
            push @{ $this->{'regexp_cache'} }, $code;
        }
        return $this->validate( $input_data );
    }
    
    return $matched;
}
[download]

ok, so it's not a complete module -- no error checks or accessors or xml loading/parsing, but that took me all of 20 minutes, so a complete version wouldn't be much extra...

just need a good DTD for the xml description... any takers???

d_i_r_t_y