Sorry, I tested it on the local server. I cant made all my experiments in the main server. So, forget about the starting memory usage & think about the hash size its growing. As you told i am posting my peice of code which i am using for reading the files.

1) I am not passing any hashes to functions. 2) I cant release the scope of that hash because I need it to write an excel at the end of the code

 foreach $file (@cdr_list)
{
    chomp $file;
    my $memgthy = `free -m | awk 'NR==2{printf " %.2f%",\$3*100/\$2 }'
+`;
    print "Memory Usage : ",$memgthy,$/;
    open (FP,"$file") or die "Could not open $file\n";
    $first=1;
    while ($line=<FP>){
        chomp $line;
        if ($first==1){
            ($sgsn_id,$x,$time,$x)=split(/\,/,$line);
            push(@sgsn_list,$sgsn_id) unless $seen_sgs{$sgsn_id}++;
            $cdr_date=substr($time,0,10);
            $single_day=substr($time,0,8);
            push (@date_list,$cdr_date) unless $seen_cdr{$cdr_date}++;
            push (@single_day_list,$single_day) unless $seen{$single_d
+ay}++;
            $first++;
        }
        else{
            #FAIL_IN_RAU_MME_TO_2GSGSN,0;
            $cmp=substr(reverse($line),0,1);
            if ($cmp eq ";") 
            {
                ($var,$value,$x)=split(/\,/,$line);
                push (@variable_list,$var) unless $seen_var{$var}++;
                $ass_val{$var}=$value;
                $pap_data{$cdr_date}{$sgsn_id}{$pap_id}=0;
                if ($mcc ne "" && length($mcc)<4){
                    $mcc_data{$cdr_date}{$sgsn_id}{$mcc}=0;
                }
                if ($mnc ne ""){
                    $mnc_data{$cdr_date}{$sgsn_id}{$mcc}{$mnc}=0;
                }
                if ($rac ne ""){
                    $rac_data{$cdr_date}{$sgsn_id}{$mcc}{$mnc}{$rac}=0
+;
                }
                if ($nsei ne ""){
                    $nsei_data{$cdr_date}{$periodic_duration}{$sgsn_id
+}{$pap_id}{$nsei}=0;
                }
                if ($nsvci ne ""){
                    $nsvci_data{$cdr_date}{$periodic_duration}{$sgsn_i
+d}{$pap_id}{$nsei}{$nsvci}=0;
                }
                foreach $var (@variable_list){    
                    $value=$ass_val{$var};
                    if ($var eq "RTT_DUR_ATTACH_MIN" || $var eq "RTT_D
+UR_ATTACH_MAX" || $var eq "PEAK_GB_PDP_Cont" || $var eq "PEAK_ATTACH_
+GB_USERS" || $var eq "PEAK_ACTIVE_SUBS_PER_PAPU" || $var eq "PEAK_ACT
+IVE_GB_PDP_CONTEXTS" || $var eq "DUR_MO_PDP_MOD_MIN" || $var eq "DUR_
+MO_PDP_MOD_MAX" || $var eq "PEAK_ATTACH_IU_USERS" || $var eq "PEAK_AC
+TIVE_IU_PDP_CONTEXTS" || $var eq "PEAK_IU_PDP_CONT" || $var eq "PEAK_
+LOAD_RATE_OF_OBJECT" || $var eq "PEAK_GB_PDP_CONT"){
                        $sgsn_name{$single_day}{$sgsn_id}{$var}{$value
+}=0;
                        $sgsn_val{$cdr_date}{$sgsn_id}{$var}{$value}=0
+;
                        $pap_val{$cdr_date}{$sgsn_id}{$pap_id}{$var}{$
+value}=0;
                        $mcc_val{$cdr_date}{$sgsn_id}{$mcc}{$mnc}{$var
+}{$value}=0;
                        $rac_val{$cdr_date}{$sgsn_id}{$mcc}{$mnc}{$rac
+}{$var}{$value}=0;
                    }
                    else {
                        if ($mcc == 405){
                            $circle_val{$single_day}{$mnc}{$var}=$valu
+e + $circle_val{$single_day}{$mnc}{$var};
                        }
                        $sgsn_name{$single_day}{$sgsn_id}{$var}=$value
+ + $sgsn_name{$single_day}{$sgsn_id}{$var};
                        $sgsn_val{$cdr_date}{$sgsn_id}{$var}=$value + 
+$sgsn_val{$cdr_date}{$sgsn_id}{$var};
                        $pap_val{$cdr_date}{$sgsn_id}{$pap_id}{$var}=$
+value + $pap_val{$cdr_date}{$sgsn_id}{$pap_id}{$var};
                        $mcc_val{$cdr_date}{$sgsn_id}{$mcc}{$mnc}{$var
+}=$value + $mcc_val{$cdr_date}{$sgsn_id}{$mcc}{$mnc}{$var};
                        $rac_val{$cdr_date}{$sgsn_id}{$mcc}{$mnc}{$rac
+}{$var}=$value + $rac_val{$cdr_date}{$sgsn_id}{$mcc}{$mnc}{$rac}{$var
+};
                        if ($var eq "IP_NSVC_PASSED_DATA_IN_BYTES"){
                            $nsvc_val{$cdr_date}{$periodic_duration}{$
+sgsn_id}{$pap_id}{$nsei}{$nsvci}{$var}=$value + $nsvc_val{$cdr_date}{
+$periodic_duration}{$sgsn_id}{$pap_id}{$nsei}{$nsvci}{$var};
                        }
                    }
                }
                @variable_list=();
                %seen_var=();
                %ass_val=();
                $pap_id="";
                $mcc="";
                $mnc="";
                $rac="";
                $nsei="";
                $nsvci="";
            }
            else {
                ($var,$value,$x)=split(/\,/,$line);
                
                if ($var eq "PAPU_INDEX"){
                    $pap_id=$value;
                }elsif ($var eq "MCC" || $var eq "IU_RA_MCC"){
                    $mcc=$value;
                }elsif ($var eq "MNC" || $var eq "IU_RA_MNC"){
                    $mnc=$value;
                }elsif ($var eq "RAC"){
                    $rac=$value;
                }elsif ($var eq "NSEI"){
                    $nsei=$value;
                }elsif ($var eq "NSVCI"){
                    $nsvci=$value;
                }elsif ($var eq "PERIOD_DURATION"){
                    $periodic_duration=$value;
                    push (@periodic_list,$periodic_duration) unless $s
+een_dur{$periodic_duration}++;
                }elsif ($var eq "OBJECT_NAME"){
                    $object_name=$value;
                    $object_data{$cdr_date}{$sgsn_id}{$object_name}=0;
                }elsif ($var eq "OBJECT_INDEX"){
                    $object_index=$value;
                    $objectindex_data{$cdr_date}{$sgsn_id}{$object_nam
+e}{$object_index}=0;
                }elsif ($var eq "PEAK_LOAD_RATE_OF_OBJECT"){
                    $peak_load_data{$cdr_date}{$sgsn_id}{$object_name}
+{$object_index}{$var}{$value}=0;
                }elsif ($var eq "AVE_LOAD_RATE_SUM" || $var eq "AVE_LO
+AD_RATE_DEN"){
                    $peak_load_data{$cdr_date}{$sgsn_id}{$object_name}
+{$object_index}{$var}= $peak_load_data{$cdr_date}{$sgsn_id}{$object_n
+ame}{$object_index}{$var} + $value;
                } else {
                    push (@variable_list,$var) unless $seen_var{$var}+
++;
                    $ass_val{$var}=$value;
                }
            }
        }
    }
    close (FP);
    FP->flush();
}

my $total_size = total_size(\%val);
print "\%val :",$total_size,$/;
my $total_size = total_size(\%seen_cdr);
print "\%seen_cdr :",$total_size,$/;
my $total_size = total_size(\%seen_var);
print "\%seen_var :",$total_size,$/;
my $total_size = total_size(\%pap_data);
print "\%pap_data :",$total_size,$/;
my $total_size = total_size(\%mcc_data);
print "%mcc_data :",$total_size,$/;
my $total_size = total_size(\%mnc_data);
print "\%mnc_data :",$total_size,$/;
my $total_size = total_size(\%sgsn_val);
print "\%sgsn_val :",$total_size,$/;
my $total_size = total_size(\%sgsn_name);
print "\%sgsn_name :",$total_size,$/;
my $total_size = total_size(\%pap_val);
print "\%pap_val :",$total_size,$/;
my $total_size = total_size(\%mcc_val);
print "\%mcc_val :",$total_size,$/;
my $total_size = total_size(\%rac_val);
print "\%rac_val :",$total_size,$/;
my $total_size = total_size(\%nsei_data);
print "\%nsei_data :",$total_size,$/;
my $total_size = total_size(\%nsvci_data);
print "\%nsvci_data :",$total_size,$/;
my $total_size = total_size(\%nsvc_val);
print "\%nsvc_val :",$total_size,$/;


my $t1 = Benchmark->new;
my $td = timediff($t1, $t0);
print "the code took:",timestr($td),"\n";
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