for my $val(@values) {
    $val = $dbh->quote($val);
    my $sth = $dbh->prepare_cached(
       "UPDATE foo SET bar=7 WHERE baz=$val"
    );
    $sth->execute();
}

##</code><code>##

for my $val(@values) {
    my $sth = $dbh->prepare_cached(
       "UPDATE foo SET bar=7 WHERE baz=?"
    );
    $sth->execute($val);
}