That's because $sthB_A is undefined. The do() method will take a prepared statement, though.

my $sthB_A = $dbh->prepare($Command_B);

my $count = 1;

foreach (@CHOICE_B[1 .. $elements_in_array_B]){
   $sthB_A->bind_param($count, $_);
   $count++;
}

my $result =  $dbh->do($sthB_A) or die "Couldn't do query: ".$dbh->err
+str;
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