Well, here's a little to get started ;-)

I am guessing, (from the code you have inherited), that you want the rows returned from the database query reported as columns - not rows. I wrote a transpose function for that. If that's not the case, then don't transpose @data.

This code could be a little sticky for a beginner, so ask questions on what you don't understand.

Note that the @col array contains the 'headers' of the data you want (in rows or columns, I don't know what is required).

These columns should be the names of the columns returned by the query (THAT you intend to be in the report) plus any additional fields you want to include, (mkt_1, profit, percent_profit, etc..).

my %ave12_cost;

while (my @row = $sth_2->fetchrow_array) {
    
    # @row has 2 items - item AND average cost for the item
    
    # remove trailing spaces    
    s/\s+$// for @row;

    # save item and average cost in a hash whose key is 'item'
    # 123.4 becomes 123.40 AND 456 becomes 456.00
    $ave12_cost{ $row[0] } = sprintf "%.2f", $row[1];
}

$sth_2->finish();

my @col = qw(
agc
market
mkt_1
analysis_code
item
customer
key_val2
key_val3
terms_code
audit_seq
aud_date
aud_time
opr_id
action
unit_price
profit
percent_profit
cur_per_month
);

my @data = [ @col ];

while (my $href = $sth_3->fetchrow_hashref) { 

    # remove trailing spaces    
    s/\s+$// for values %$href;
    
    # do calculations    
    $href->{mkt_1} = substr($href->{market}, 0, 1) == 1 ? "A&D" : "MCP
+";
    $href->{profit} = $href->{unit_price} - $ave12_cost{$href->{item}}
+;
    $href->{percent_profit} = sprintf "%.1f", ($href->{profit} / $href
+->{unit_price}) * 100;
    . . . .
    
    # add to an array for output to Excel
    # (Data added in order of '@col' array)
    push @data, [ @$href{ @col } ];
}

$sth_3->finish();

my @transposed = transpose( @data );

my $file = 'sales.csv';
open my $out, ">", $file or die "Unable to create $file. $!";

# print to CSV file
for my $row (@transposed) {
    print $out join(",", @$row), "\n";
}

close $out or die "Unable to close $file. $!";


sub transpose {
    my (@data, @trans) = @_;
    for my $r (0 .. $#data) {
        for my $c (0 .. $#{ $data[$r] }) {
            $trans[$c][$r] = $data[$r][$c];
        }
    }
    return @trans;
}
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Just out of curiosity, why are you rewriting the code? Does it still work, (even if it's not the best/most pretty)?

If there are embedded commas in any of the fields, the print to the file will fail. The statement print $out join(",", @$row), "\n"; would have to be replaced by a method from a module like Text::CSV_XS.