@dates = `mysqlshow --password=\'xxxxxxx\' pzbg001`;
shift @dates;
shift @dates;
shift @dates;
shift @dates;
pop @dates;

foreach $date(@dates){
        chomp $date;
        $date =~ s/ //g;
        $date =~ s/\|//g;
        $date =~ s/\-//g;
        $date =~ s/Tables//g;
        $date =~ s/\+//g;
...

##</code><code>##

@dates = map { /^\|\s+([\d_]+)\s+\|$/ } `mysqlshow --...`

##</code><code>##

   $query = "select $result from $date where inintf=$inint";

##</code><code>##

# get the list of tables (table names are \d+_\d+_\d+):
my @dates = map { /^\|\s+([\d_]+)\s+\|$/ } `mysqlshow --...`

# 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 $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 @data, [ $date, $octets/(1024*1024) ];
}

# do all that other GD stuff... then:

my $myimage = $mygraph->plot(\@data) or die $mygraph->error;

# and on to the web page...