$dbh->do(
   'UPDATE INV SET SALESMAN = ? WHERE CODE = ?',
   undef, $SALESMAN, $CODE,
);

##</code><code>##

my $dbh = DBI->connect(
   $data_source, $username, $pass,
   {RaiseError => 1},
);

##</code><code>##

my $updy="Y";
$dbh->do("UPDATE INV SET SOLD=$updy  ... ");

##</code><code>##

$dbh->do("UPDATE INV SET SOLD='$updy'  ... ");

##</code><code>##

$dbh->do("UPDATE INV SET SOLD = ? WHERE CODE = ?", undef,$updy,$CODE);