my $sth = $dbh -> prepare("insert into table1 (col1, col2, col2) values (?, ?, ?)");

##</code><code>##

# do we need an insert or an update?
my $row_checker = $dbh -> prepare("select count(col1) from table1 where col1 = ? and col2 = ? and
 col3 = ?");
my $inserter = $dbh -> prepare("insert into table1 (col1, col2, col2) values (?, ?, ?)");my $upda
ter = $dbh -> parepare("update table1 set col1 = ?, col2 = ?, col3 = ? where col1 = ? and col2 = 
? and col3 = ?");

##</code><code>##

my $row_checker = "select count(col1) from table1 where col1 = ? and col2 = ? and col3 = ?";
$row_checker = $dbh -> prepare($row_checker);

# or ...

my $updater = $dbh -> prepare(qq{ 
        update table1 set col1 = ?, col2 = ?, col3 = ?
                where col1 = ? and col2 = ? and col3 = ?
});

##</code><code>##

my $rowRef = $dbh -> selectrow_arrayref("select col1 from table1 where col1 = col2 and col2 != '$
someval'");
my @row = @{ $rowRef };
#or ...
my $tuple = shift @{ $rowRef };
#or ...
my $tuple = @{ $rowRef }[0];

##</code><code>##

my ($tuple) = map { @{ $_ } } $dbh -> selectall_arrayref("select col1 from table1 where col1 = co
l2 and col2 != '$someval'");

##</code><code>##

if ($tuple) { # succeeded...

##</code><code>##

my $next_col1 = "select distinct(col1) from table1";
$next_col1 = $dbh -> prepare($next_col1);
$next_col1 -> execute();

my @col1s = map { @{ $_ } } @{ $next_col1 -> fetchall_arrayref() };

foreach my $col1 (@col1s) { ...