求助:用perl脚本调用rrdtool绘图．．．（在线等．．．．．．．）

我是想用perl脚本来调rrdtool绘图，网上找来的代码如下，但是我运行时有错，说下面红色标记的那一行＂Use of uninitialized value in addition (+) at graph.pl line 42.＂，＂problem generating the graph: 'SCALAR' is not a valid function name＂，初学者不知道哪里有错，请高手看一下这个代码指点一下，感激不尽！
#!/usr/bin/perl -w
# This script fetches data from target.rrd, creates a graph of memory
# consumption on the target (Dual P3 Processor 1 GHz, 656 MB RAM)

# call the RRD perl module
use lib qw( /usr/local/rrdtool-1.0.41/lib/perl ../lib/perl );
use RRDs;
my $cur_time = time();                # set current time
my $end_time = $cur_time - 86400;     # set end time to 24 hours ago
my $start_time = $end_time - 2592000; # set start 30 days in the past

# fetch average values from the RRD database between start and end time
my ($start,$step,$ds_names,$data) = RRDs::fetch("target.rrd", "AVERAGE",
                "-r", "600", "-s", "$start_time", "-e", "$end_time");
# save fetched values in a 2-dimensional array
my $rows = 0;
my $columns = 0;
my $time_variable = $start;
foreach $line (@$data) {
  $vals[$rows][$columns] = $time_variable;
  $time_variable = $time_variable + $step;
  foreach $val (@$line) {
          $vals[$rows][++$columns] = $val;}
  $rows++;
  $columns = 0;
}
my $tot_time = 0;
my $count = 0;
# save the values from the 2-dimensional into a 1-dimensional array
for $i ( 0 .. $#vals ) {
    $tot_mem[$count] = $vals[$i][1];
    $count++;
}
my $tot_mem_sum = 0;
# calculate the total of all values
for $i ( 0 .. ($count-1) ) {
    $tot_mem_sum = $tot_mem_sum + $tot_mem[$i];}
# calculate the average of the array
my $tot_mem_ave = $tot_mem_sum/($count);
# create the graph
RRDs::graph ("/images/mem_$count.png",   \
            "--title= Memory Usage",    \
            "--vertical-label=Memory Consumption (MB)", \
            "--start=$start_time",      \
            "--end=$end_time",          \
            "--color=BACK#CCCCCC",      \
            "--color=CANVAS#CCFFFF",    \
            "--color=SHADEB#9999CC",    \
            "--height=125",             \
            "--upper-limit=656",        \
            "--lower-limit=0",          \
            "--rigid",                  \
"--base=1024",              \
            "DEF:tot_mem=target.rrd:mem:AVERAGE", \
            "CDEF:tot_mem_cor=tot_mem,0,671744,LIMIT,UN,0,tot_mem,IF,1024,/",\
            "CDEF:machine_mem=tot_mem,656,+,tot_mem,-",\
            "COMMENT:Memory Consumption between $start_time",\
            "COMMENT:    and $end_time                     ",\
            "HRULE:656#000000:Maximum Available Memory - 656 MB",\
            "AREA:machine_mem#CCFFFF:Memory Unused",   \
            "AREA:tot_mem_cor#6699CC:Total memory consumed in MB");
my $err=RRDs::error;
if ($err) {print "problem generating the graph: $err\n";}
# print the output
print "Average memory consumption is ";
printf "%5.2f",$tot_mem_ave/1024;
print " MB. Graphical representation can be found at /images/mem_$count.png.";

$tot_mem[$i]
这个可能包含了没有被initialize的数据...
请检查他的长度跟$count一样..每个element都有数据...

在那之前的那个循环里已经赋值了啊，for $i ( 0 .. $#vals ) {
    $tot_mem[$count] = $vals[$i][1];
    $count++;
}

而且这种错误是每个循环都一句＂Use of uninitialized for　value in addition (+) at graph.pl line 42.＂
我怀疑过for(０．．$#vals)中多了一个，改成for(０．．$#vals－１)还是不对，继续求助，谢谢楼上的大哥啊

to avoid warning "Use of uninitialized ..." , simply switch -w off in the top line:
#!/usr/bin/perl

or initial the array @tot_mem:
my @tot_mem = ();

-- ulmer

switch -w off in the top linek
however,the second way cannot work.
there is an error : "problem generating the graph: 'SCALAR' is not a valid function name"

i want to know the reason,who can tell me?

thanks!