I would go for 5:

5. Keep the official enumeration in the database; query the database to generate code that contains appropriate constants/enums. Have to make sure your code generation really occurs when the database changes. Could automate this as part of the build/test process.

But please note that you don't need to do this as part of the build/test process, but you can also do this at compile time in a BEGIN block.

BEGIN {
    use DBI;
    my $dbh = DBI->connect( dsn,user,password );
    my $result = $dbh->some sort of query that generates name/value pa
+irs;
    no strict 'refs'; # allow for using variables to make subs
    foreach (@$result) {
        *{$_->[0]} = eval "sub () { $_->[1] }"; # use constant on vari
+ables
    }
}
[download]

That should ensure that your constants are up to date for each run, as opposed to each build/test cycle.

Liz

Update:
As thor pointed out, this could be construed as going with #4, but I was more thinking along the lines of SHOW COLUMNS FROM table LIKE 'columnname' and associated magic as can e.g. be found on the MySQL site.