my $sql = q{SELECT * FROM tblX WHERE condition = ?};

$sth = $dbh->prepare($sql);
$sth->execute($value_to_sub_for_question_mark);


##</code><code>##

my $sql = q{SELECT * FROM tblX WHERE condition1 = ? and condition2 = ?};
my $sth = $dbh->prepare($sql);
$sth->execute(@array);