Tonight I will at last sleep well! Your code failed and my code failed but a hybrid of the two works perfectly! Ubi Concordia Ibi Victoria indeed! The code below works without problem and prints out the graph that I am ever so happy to see!

Thank you so much again for your help! Code as follows:

#!/usr/bin/perl


use CGI ':standard';
use GD::Graph::lines;
use DBI;
use Data::Dumper;
use Mysql;

$inint = "1";
$result = "sum(octets)";

my $dbh = Mysql->connect('localhost','pzbg001','root','xxxxxxx');

@dates = $dbh->ListTables;




# query each table for sum of traffic,
# push table_name (i.e. date) and traffic sum onto @data:
my @data = ();
for my $date ( @dates ) {
    my $dbh = DBI->connect('DBI:mysql:pzbg001', 'root', 'xxxxxxx', {Ra
+iseError => 1});
    my $query = "select $result from $date where inintf=$inint";
    my $sth = $dbh->prepare($query);
    if (!$sth) { die "Illegal query: $query" };
    $sth->execute;
    my $octets = ($sth->fetchrow_array)[0]; # don't chomp it!
    $sth->finish;
    push (@total, $octets/(1024*1024));
}

my @data = ( \@dates, \@total);




#####################

my $mygraph = GD::Graph::lines->new(600, 300);
$mygraph->set(
x_label => 'Date',
y_label => 'Kb of Traffic',
title => 'Traffic for $router ',


# Draw datasets in 'solid', 'dashed' and 'dotted-dashed' lines
line_types => [1],

# Set the thickness of line
line_width => 2,

# Set colors for datasets
dclrs => ['blue'],

) or warn $mygraph->error;
$mygraph->set_legend_font(GD::gdMediumBoldFont);
$mygraph->set_legend('Total');
my $myimage = $mygraph->plot(\@data) or die $mygraph->error;
print "Content-type: image/png\n\n";
print $myimage->png;
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Baiul

Ubi Concordia Ibi Victoria