Hi.. Thanks for the reply. Below is the minimum code. In this part records of 1gb i/p file(AH) is processed in such a way that they take the form of a hash reference. Now values of field 'bidirVolume' is stored in a new array AccUsage.

 my $AccUsg;

while(<AH>) {
  chomp;
  my $line=$_;
  $AccuCount++;
  my $MobileNumber;

  if( $line =~ /subscriberId:(\w+)\(\"(\d+)\"\)/ ) {
    $MobileNumber=$2;
  }

  my $plan=$line;
  $plan =~s/\\//g;

  my @AccVolume;

  if ( $plan =~ /usageControlAccum:(\w+)\(\"(.*)\"\)/ ) {
        my $p=$2;
        $p=~s/:\{/ => {/g;
        $p=~s/:\[/ => [/g;
        $p=~s/\"/\'/g;
        $p=~s/\':/\'=>/g;
        $p=~s/\}n/\}/g;

        #print $p,"\n";
        my $e=eval($p);

        if ( @$ ) {
          push (@AccVolume,"error");
        } else {
        #print Dumper($e);
          foreach my $value ( @{$e->{'reportingGroups'}} ) {
            if ( exists ( $value->{'absoluteAccumulated'}->{'counters'
+} ) ) {
              $AccUsg->{$MobileNumber}->{$value->{'subscriberGroupName
+'}}=$value->{'absoluteAccumulated'}->{'counters'}->[0]->{'bidirVolume
+'};
            } elsif ( exists ( $value->{'absoluteAccumulated'}->{'bidi
+rVolume'} ) ) {
              $AccUsg->{$MobileNumber}->{$value->{'subscriberGroupName
+'}}=$value->{'absoluteAccumulated'}->{'bidirVolume'};
            }
          }
    }
  }
}
close(AH);
[download]

Now the the second 16gb i/p file (FH) matches its $planname value with the AccUsage hash and print the matched value to the output file.

while(<FH>) {
  chomp;
  my $line=$_;
  $SubsCount++;
  my $msisdn;
  my $IMEI;
  my $Circle;
  my $DeviceType;
  my $OPTIN;
  my $PlanType;
  my $familyId;
  my $trafficIds;

  if($line=~/userId:S(\d+)\(\"(\w+)\"\)/) {
    $msisdn = $2;
  }

  if ( $line=~/operatorInfo:A(\d+)\[(.*?)\]/ ) {
    my $opcinfo=$2;
        #ix0:S13("OptInState:3G")ix1:S11("CircleId:MH")ix2:S8("DevType
+:")ix3:S9("imei:NULL")ix4:S16("PlanType:prepaid")
        #print $opcinfo,"\n";
        if( $opcinfo =~ /ix(\d+):S(\d+)\(\"imei:(\w*)\"\)/ ) {
          $IMEI=$3;
        }
        if( $opcinfo =~ /ix(\d+):S(\d+)\(\"OptInState:(\w*)\"\)/ ) {
          $OPTIN=$3;
        }
        if( $opcinfo =~ /ix(\d+):S(\d+)\(\"CircleId:(\w*)\"\)/ ) {
          $Circle=$3;
                  if( exists ( $lookup->{$Circle} ) ) {
                    $Circle=$lookup->{$Circle};
                  }
        }
        if( $opcinfo =~ /ix(\d+):S(\d+)\(\"DevType:(\w*)\"\)/ ) {
          $DeviceType=$3;
        }
        if( $opcinfo =~ /ix(\d+):S(\d+)\(\"PlanType:(\w*)\"\)/ ) {
          $PlanType=$3;
        }



  }

  my @ValidPlan;
  #groups:A1[ix0:S10("3BASIC:100")]
  if($line=~/groups:A(\d+)\[(.*?)\]/) {
    my $plans=$2;
        my @AllPlans = split('ix\d+:S\d+\("',$plans);

        #print Dumper($AccUsg->{$msisdn});

        foreach my $p ( @AllPlans ) {
          $p =~ s/\"\)//g;
          if ($p eq "" ) { next; }
          #my @planname=split(":",$p);

                  if ( $p =~ /(\w+):(\d+)[:]?(.*)/) {
                    my $planname=$1;
                        my $priority=$2;
                        my $expdate=$3;

                        $expdate =~ s/,/\;/g;

            if( exists ( $AccUsg->{$msisdn}->{$planname} ) ) {
                  if ( $expdate eq "") {
                  push(@ValidPlan,"$planname;$priority;;;$AccUsg->{$ms
+isdn}->{$planname}"); }

                  elsif ( length($expdate) > 19 ) {
                  push(@ValidPlan,"$planname;$priority;$expdate;$AccUs
+g->{$msisdn}->{$planname}"); }

                  else {
                  push(@ValidPlan,"$planname;$priority;$expdate;;$AccU
+sg->{$msisdn}->{$planname}"); }

                 } else {
                          if( $expdate eq "") {
                            push(@ValidPlan,"$planname;$priority;;;");
                          } else {
                            if( length($expdate) > 19 ) {
                              push(@ValidPlan,"$planname;$priority;$ex
+pdate;");
                                } else {
                                  push(@ValidPlan,"$planname;$priority
+;$expdate;;");
                                }
                          }

            }

                  }


        }
  }


  if ( $line=~/familyId:S(\d+)\(\"(.*?)\"\)/ ) {
    $familyId=$2;
  }
  if ( $line=~/trafficIds:A(\d+)\[(.*?)\]/ ) {
    $trafficIds=$2;
  }

#Now sorting the printplans priority wise
  #  my $printPlan=join("|",@ValidPlan);
  my @validPlanSorted = sort { ($b =~ /(.*?);(\d+);(.*?)/)[1] <=> ($a 
+=~ /(.*?);(\d+);(.*?)/)[1] } @ValidPlan;
  my $printPlan=join("|",@validPlanSorted);
  $finalCount++;

  #print OUT "$msisdn;$IMEI;$Circle;$DeviceType;$OPTIN;$PlanType;$fami
+lyId;$trafficIds;$printPlan\n";
  print OUT "$msisdn,$IMEI,$Circle,$DeviceType,$OPTIN,$PlanType,$print
+Plan\n";

}
close(FH);
[download]

where one record of AH

P[containerVrsn:U(0)recordVrsn:U(0)size:U(560)ownGid:G[mdp:U(111817893
+5)seqNo:U(55)]logicalDbNo:U(1)classVrsn:U(1)timeStamp:U(0)dbRecord:T[
+classNo:U(1091971)size:U(532)updateVersion:U(1157)checksum:U(13183789
+05)EPC_UsageControlAccumulatedPot:R[subscriberId:S12("918970692483")u
+sageControlAccum:S543("{\"reportingGroups\":[{\"absoluteAccumulated\"
+:{\"counters\":[{\"bidirVolume\":3022011787,\"name\":\"base\"}],\"exp
+iryDate\":{\"volume\":\"25-05-2013T00:00:00\"},\"previousExpiryDate\"
+:{\"time\":\"25-04-2013T00:00:00\",\"volume\":\"25-04-2013T00:00:00\"
+},\"reportingLevel\":\"totalTraffic\",\"resetPeriod\":{\"volume\":\"3
+0 days\"}},\"name\":\"110\",\"restartInfo\":\"25-04-2013T00:00:00\",\
+"selected\":\"no\",\"subscriberGroupName\":\"KA_FUP_2G80K_30\",\"subs
+criptionDate\":\"25-04-2013T00:00:00\",\"validityTime\":1800}],\"vers
+ion\":\"2.0\"}")]]]
[download]

where one record of FH

P[containerVrsn:U(0)recordVrsn:U(0)size:U(276)ownGid:G[mdp:U(109017151
+1)seqNo:U(28)]logicalDbNo:U(1)classVrsn:U(1)timeStamp:U(0)dbRecord:T[
+classNo:U(1064620)size:U(248)updateVersion:U(5)checksum:U(928324968)E
+PC_SubscriberPot:R[userId:S12("919902995746")groups:A1[ix0:S12("KA_BA
+SIC:100")]services:A0[]blacklist_services:A0[]operatorInfo:A5[ix0:S21
+("HomeMNC1:DefaultValue")ix1:S11("CircleId:KA")ix2:S13("OptInState:2G
+")ix3:S9("imei:NULL")ix4:S16("PlanType:prepaid")]pccSubscriberPotRef:
+M0[]notificationData:A0[]familyId:S0("")trafficIds:A0[]]]]
[download]

where one record of output file

MSISDN,IMEI,Circle,DeviceType,OPTIN,PlanType,PACKID1;priority;startdat
+e;enddate;AccumulateUsage|PACKID2;priority;startdate;enddate;Accumula
+teUsage|PACKID3;priorit
y;startdate;enddate;AccumulateUsage|PACKID4;priority;startdate;enddate
+;AccumulateUsage|
919164032638,NULL,KA,,2G,prepaid,KA_BASIC;100;;;|KA_FUP_2G80K_30;90;22
+-08-2014T00:00:00;20-09-2014T23:59:59;7032609129
[download]

Now I need to add four more fields from AH file (counter, expiry_date, prev_expirydate_volume & prev_expirydate_time) for this I need to add more AccUsage type hashes which are causing memory issue..so how much memory it will need more? I know code is badly written but thats how it is running here in production for few years now..& i can't help it :) ... thanks a lot