my $sth = $dbh->prepare( 'SELECT count(*) FROM num_table WHERE num = ?' );
foreach my $n ( @num_from_doc ) {
    $sth->execute( $n );
    my ($exists) = $sth->fetchrow_array;
    my $not = $exists ? '' : ' not';
    print "Number $n is$not in the database.\n";
}