Just switch to blocking objects. Alternatively, you can fork off one subnet at a time to a child process and its memory will get reclaimed when it exits.

actually, if blocking mode is set i cant use callbacks, they only work at non-blocking mode. im really very inexperienced in fork. could u give me an example for that?? also, is it possible to specify for number process at a time instead of using the subnet for regulating these?. Btw, the reason i said that 60mb is too much, is because it hasnt done the Real Job yet, which would be to store the data in variables then print it, but if just for scanning and receiving timeouts im using 60mb i can only wonder how much it will take after it stars receiving data.

Try it this way. Create a set number of sessions, then dispatch events (using snmp_dispatch_once()) until you get a reply. Then create another and dispatch events until you get another reply, and so on. Adjust the value of $MAXCONCURRENT to control your memory usage.

(Note:Untested code):

#!/usr/bin/perl -w
use warnings;
use strict;
use Net::IP;
use Net::SNMP qw( snmp_dispatch_once oid_lex_sort );
#use Smart::Comments '###';

my $startip     = $ARGV[0] || die "Missing Starting IP";
my $endip       = $ARGV[1] || die "Missing Ending IP";
my $community   = $ARGV[2] || die "Missing community string";

my $ips = Net::IP->new( "$ARGV[ 0 ] - $ARGV[ 1 ]" );

my $MAXCONCURRENT = 50;
my $running = 0;

### Updated do{} while (taken from docs) to while(){} per reply.
while( ++$ips ) { 
    my( $session, $error ) = Net::SNMP->session(
        -hostname       => $ips->ip,
        -version        => 'snmpv2c',
        -nonblocking    =>  1,
        -community      => "$community",
        -timeout        =>  3,
        -retries        =>  1,
    );

    if( defined( $session ) ) {
        my $serialno    = '.1.3.6.1.3.83.1.1.4.0';
        my $mac         = '.1.3.6.1.2.1.2.2.1.6.2';
        my @msoids      = ( $mac, $serialno );
        my $result = $session->get_request(
            -varbindlist    =>  \@msoids,
            -callback        =>  [ \&getms, $session, $ips->ip ]
        );

        $running++; ## Count the sessions started
    }else{
        warn "Session not defined for %s: %s\n", $ips->ip, $session->e
+rror_status;
    };

    ## start another unless we have the max running
    next unless $running > $MAXCONCURRENT;

    ## Dispatch events until we get a reply from one
    snmp_dispatch_once() while $running > $MAXCONCURRENT;

} 

exit;

sub getms {
    my $obj = shift;
    my $session = shift;
    my $hfcip = shift;

    $running--; ## One more done

    if (!defined($obj->var_bind_list)) {
        warn "$hfcip SNMP Error.", $obj->error_status,"\n";
        return;
    }
    ## print values for the oids
    
    $session->close;
}
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