With the exception of a spelling mistake this works very well. Thanks. If you enjoyed working out that, or for those that would like another go, I have have another bit of code along similar lines. As follows:

sub calculating_pop_summations_B {

 

  my $sthZK_B = $dbh->prepare("

 SELECT DISTINCT Aggregated_area
 FROM Geo_postaggregated_pop_count;

          ") or die "Couldn't prepare query: ".$dbh->errstr;
  $sthZK_B->execute() or die "Couldn't execute query: ".$sthZK_B->errs
+tr;

  my @sthZK_B_A_array;

  while ( my @columns_B = $sthZK_B->fetchrow() ) {

    my $Aggregated_area = $columns_B[0];

 
    my $sthZK_B_A = "

 UPDATE Geo_postaggregated_pop_count
            SET Sum_of_person_count = (

 SELECT DISTINCT (SELECT SUM(G.Person_count)
            FROM Geo_postaggregated_pop_count G
            WHERE G.Sex = 1 AND G.Aggregated_area LIKE '".$Aggregated_
+area."')+
 (SELECT SUM(G.Person_count)
            FROM Geo_postaggregated_pop_count G
            WHERE G.Sex = 2 AND G.Aggregated_area LIKE '".$Aggregated_
+area."')
 FROM Geo_postaggregated_pop_count G
            WHERE G.Aggregated_area LIKE '".$Aggregated_area."')
 FROM Geo_postaggregated_pop_count G
            WHERE G.Aggregated_area LIKE '".$Aggregated_area."'


";

    push (@sthZK_B_A_array, $sthZK_B_A);

  }
  
  
  foreach (@sthZK_B_A_array){

    
    my $sthZK_C = $dbh->prepare("
             ".$_."
          ") or die "Couldn't prepare query: ".$dbh->errstr;
    $sthZK_C->execute() or die "Couldn't execute query: ".$sthZK_C->er
+rstr; 
  }


}
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