Try this cut down version of your program on both working and non-working systems and compare the contents of $ENV{'PATH'}

#!/usr/bin/perl
use strict;
use warnings;
use CGI ':standard';
use CGI::Carp 'fatalsToBrowser';

my $node = param('node');
my $target      = "raksan";
my $wwwpath     = '/target';
my $wwwrealpath = "/home/nagios/stat/$target/htdocs";
my $tmpgraph    = "rrd-$$.gif";
my $recenttimes = time - 3600 * 36;

print header(),start_html();

my $cmd = "/home/nagios/stat/scripts/ng_rrd2img.sh $target $node dig $
+recenttimes now 300 130 > $wwwrealpath/tmp/$tmpgraph";
my $status = system($cmd);
if ($status){
  warn "$?";
}

my $path = join "\n",split ';',$ENV{'PATH'};
print qq!<pre>$cmd</pre>
<pre>PATH
$path</pre>
<img src="$wwwpath/tmp/$tmpgraph" alt="$wwwpath/tmp/$tmpgraph" border=
+"1"/>!;
print end_html();
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