UCD-SNMP-MIB::memIndex.0 = INTEGER: 0
UCD-SNMP-MIB::memErrorName.0 = STRING: swap
UCD-SNMP-MIB::memTotalSwap.0 = INTEGER: 8385920 kB
UCD-SNMP-MIB::memAvailSwap.0 = INTEGER: 8385920 kB
UCD-SNMP-MIB::memTotalReal.0 = INTEGER: 8240104 kB
UCD-SNMP-MIB::memAvailReal.0 = INTEGER: 2576224 kB
UCD-SNMP-MIB::memTotalFree.0 = INTEGER: 10962144 kB
UCD-SNMP-MIB::memMinimumSwap.0 = INTEGER: 16000 kB
UCD-SNMP-MIB::memBuffer.0 = INTEGER: 326776 kB
UCD-SNMP-MIB::memCached.0 = INTEGER: 4740904 kB
[download]

#!C:\Dwimperl\perl\bin 

use strict;
use warnings;
use Net::SNMP;
use Nagios::Plugin;
use nagios::Plugin::Getopt;
use Math::Round;


my $np;

$np=Nagios::Plugin->new(
    usage         => "Usage: %s -H <host> -C <community> -w <warn> -c 
+<crit>",
    shortname    => "SNMP Memory",
    timeout        => 5,
    blurb         => "this plugin calculates the real used memory in l
+inux which includes the cache and buffers",
    extra         => "
    Examples: 
    
    check_snmp_mem.pl -H 127.0.0.1 -C public -w 90 -c 95
    
    
    "
);

# plugin arguments
$np->add_arg(
    spec        => "host|H=s",
    help        => "ip address or hostname of device",
    required    => 1,
);

$np->add_arg(
    spec        => "community|C=s",
    help        => "snmp community string",
    required    => 1,
);

$np->add_arg(
    spec        => "warning|w=i",
    help        => "usage in percent, when a WARNING is returned",
    required    => 1,
);

$np->add_arg(
    spec        => "critical|c=i",
    help        => " mem usage in percent, when a CRITICAL is returned
+",
    required    => 1,
);

$np->getopts;

# perform sanity checking on command line options
if ( (defined $np->opts->warning) && ($np->opts->warning < 0 || $np->o
+pts->warning > 100) )  {
    $np->nagios_die( " invalid number supplied for the -w option: ente
+r a value between 0 and 100 " );
}

if ( (defined $np->opts->warning) && ($np->opts->critical < 0 || $np->
+opts->critical > 100) )  {
    $np->nagios_die( " invalid number supplied for the -c option: ente
+r a value between 0 and 100 " );
}

if ( (defined $np->opts->warning) && ( $np->opts->warning > $np->opts-
+>critical) ) {
    $np->nagios_die( " invalid number supplied for the -w option: warn
+ing threshold should be smaller than critical threshold " );
}

my $memRealTotalOID = '.1.3.6.1.4.1.2021.4.5.0';
my $memRealFreeOID = '.1.3.6.1.4.1.2021.4.6.0';
my $memRealCachedOID = '.1.3.6.1.4.1.2021.4.15.0';
my $memRealBuffersOID = '.1.3.6.1.4.1.2021.4.14.0';

my ($session, $error) = Net::SNMP->session(
     -hostname  => $np->opts->host,
     -community => $np->opts->community,
   );

   if (!defined $session) {
      $np->nagios_exit (WARNING, $error)
      #printf "ERROR: %s.\n", $error;
   }

   my $memRealFree = $session->get_request(-varbindlist => [ $memRealF
+reeOID],);
   my $memRealTotal = $session->get_request(-varbindlist => [ $memReal
+TotalOID],);
   my $memRealCached = $session->get_request(-varbindlist => [ $memRea
+lCachedOID],);
   my $memRealBuffers = $session->get_request(-varbindlist => [ $memRe
+alBuffersOID],);

$session->close();

   my $buffers = $memRealBuffers->{$memRealBuffersOID}; 
   my $cache = $memRealCached->{$memRealCachedOID};
   my $total=  $memRealTotal->{$memRealTotalOID};
   my $free = $memRealFree->{$memRealFreeOID};
   
   my $memRealUsed = $total - $free;
   my $memRealUsedMB = round ($memRealUsed / 1024);
   my $totalMB = round($total / 1024);
  
   
  my $realTPercent = (($memRealUsed - $buffers - $cache)/ $total) * 10
+0;
  my $realPercent = sprintf "%.2f", $realTPercent;
  
  
 
$np->add_perfdata(
    label    =>    "Free",
    value    =>    $free,
    uom        =>    "KB"
);

$np->add_perfdata(
    label    =>    "Total",
    value    =>    $total,
    uom        =>    "KB"
);

$np->add_perfdata(
    label    =>    "Cached",
    value    =>    $cache,
    uom        =>    "KB"
);

$np->add_perfdata(
    label    =>    "Buffered",
    value    =>    $buffers,
    uom        =>    "KB"
);


 #####################################################################
+#########
# check the result against the defined warning and critical thresholds
+,
# output the result and exit
$np->nagios_exit( 
     return_code => $np->check_threshold($realPercent), 
     message => " used: $realPercent% with $memRealUsedMB MB of $total
+MB MB free" 
);
[download]

Surely I don't understand the question - it looks like you are asking how to eliminate e.g. the $cache variable, but that seems too simple given your apparently higher skill level.!

One world, one people