Well, MySQL is very capable of checking the format itself. Why not do something like:

eval {
    local $dbh -> {RaiseError} = 1;
    local $dbh -> {PrintError} = 0;
    local $dbh -> {AutoCommit} = 0;

    my $sql = "INSERT INTO foo_table VALUES (?, ?)";
    my $sth = $dbh -> prepare ($sql);
    $sth -> execute ($key, $date);
};
if ($@) {
    # Some error occurred, for instance due to wrong dateformat.
    $dbh -> rollback;
    # Inspect $@ for error, take appropriate action.
    ...
}
else {
    $dbh -> commit;
}
[download]

Abigail