my @_id = $cgi->params('id');

error_exit("You must select at least one ID.")
    unless @_id;

my @id;

for(@_id) {
    my ($match) = /\A(\d{5,9}[ABC])\z/;

    error_exit("Invalid ID: $_")
        unless defined $match;

    push @id, $match;    
}

##</code><code>##

my $validator = Data::FormValidator->new({
    delete_items_page => {
        required => [qw(id .. ..)],
        constraints => {
            id => '/\A(\d{5,9}[ABC])\z/',
            # ..
        },
    },
});