Using Data::Dumper I print @SQLvars like so, before executing the query

warn Dumper \@SQLvars;
[download]

I see the array printed, with 4 items in each row of the array, like this

$VAR1 = [
          {
            'COLX' => 'TESTA1',
            'COLY' => 'TESTA2',
            'COLZ' => 'TESTA3'
          },
          {
            'COLX' => 'TESTB1',
            'COLY' => 'TESTB2',
            'COLZ' => 'TESTB4'
          },
[download]

I then execute the query

my $sth = $dbh->prepare($SQLQueryString);
my $array_ref = $dbh->selectall_arrayref( $SQLQueryString, { Slice => 
+{} }, @SQLvars );
[download]

Which returns this error

DBD::Oracle::db selectall_arrayref failed: called with 9 bind variable
+s when 3 are needed
[download]

For the life of me I can't work out why it thinks there should be 9. If you or anyone else can advise that'd we great.