Requete sql "update" in perl

my $sth = $db->prepare('select idS from ocs.Storage where name like ? ');
$sth->bind_param(1,"$v4");
$sth->execute();
if ($sth->rows < 0)
{
print " sorry";
}
else
{
#print "found \n",$sth->rows;
 while (my $results = $sth-> fetchrow_hashref)
  {
    $idSt = $results->{idS};
  print "idst est $idSt et vm name est $test3[$d]";
  $idSt=~ s/^\s+|\s+$//;
  $idSt=~ s/\'//g;
  $idSt=~ s/\'//g;
  $idSt=~ s/\"//g;
  $idSt=~ s/^\s+//;
  $idSt=~ s/\s+$//;
  my $null=0;
  $idSt=$idSt +$null;
  my $statement1 = "UPDATE VM SET stoaregeA_id = ? where VM_OS = ?";
  $db5->do($statement1,undef,$idSt,$test3[$d]);
}}