Here a demonstration:

use strict;
use warnings;

my $count=0;


while (<DATA>) {
    if ( /^<13>/ .. /^END OF REPORT$/ ){
        if (/\*\sparameters after change\s\=/ .. /\*\sNRG location\s\=
+/) { 
            print "$count: $_";
        }
    } else {
        $count++
    }
}
__DATA__
<13>Nov 13 17:27:25 OamCOMM[12260]:
TIMESTAMP=Tue Nov 13 17:27:25 2018

MSGCLS=OAMOPE
Title=OAM Create OPERATION
Severity=Inform
message={username:xxxx@::xxxx:xxx.xxx.xxx.x;
 causeDISTINGUISH_NAME=epsProfileId=xxxxx,pSProfileDataId=x,subscripti
+onProfileD
+ataId=x,managedElementId=xxxx
USER_LABEL=
******************* parameters after change =*******************
epsMaxRequestedBandwidthUL=xxxxxxxxx
epsMaxRequestedBandwidthDL=xxxxxxxxx
epsQosAllocRetPrioVulnerabilit=xxxxxxx
epsQosAllocRetPrioCapability=xxxxxxx
epsQosAllocRetPrioLevel=xxxxxxxxx
epsQosClassId=xxxxxx
sessionTimeout=xxxxxxx
idleTimeout=xxxx
epsChargingCharacteristics=xxxxxx
epsVplmnDynamicAddrAllowed=xxxxxxxxxx
epsGwAllocType=xxxxxx
epsPdnType=xxxxxx
epsAccessPointName=xxxxxx.xxxxxxx
******************* NRG location =*******************
NRG_KEY=x
}
Message Id=10011
END OF REPORT

<13>Nov 13 17:27:25 OamCOMM[12260]:
TIMESTAMP=Tue Nov 13 17:27:25 2018

MSGCLS=OAMOPE
Title=OAM Create OPERATION
Severity=Inform
message={username:xxxx@::xxxx:xxx.xxx.xxx.x;
 causeDISTINGUISH_NAME=packetDataProtocolProfileId=xxxxx,gPacketProtoc
+olProfileD
+ataId=x,pSProfileDataId=x,subscriptionProfileDataId=x,managedElementI
+d=xxxx
USER_LABEL=
******************* parameters after change =*******************
meanThroughPutClass=xxxxxx
peakThroughPutClass=xxxxx
reliabilityClass=xxxx
delayClass=xxxx
precedenceClass=xxxxx
hSDPAguaranteeFlag=x
hSUPAguaranteeFlag=x
hSUPAflag=x
hSDPAflag=x
downlinkGuaranteedBR=xxx
uplinkGuaranteedBR=xx
trafficHandlingPriority=xxxxxxx
transferDelay=xx
ratioSduError=xxxx
residualBER=xxxx
downlinkMaxBR=xxx
uplinkMaxBR=xx
maxSduSize=xxx
deliveryOfErroneousSdu=xx
deliveryOrder=xx
trafficClass=xxxxxxxx
priorityOfUmtsBearer=xxxxxxx
vplmnAddressAllowedFlag=x
pdpChargingCharacteristic=xxxxxx
accessPointName=xxxxxx.xxxxxxx
pdpType=xxxx
******************* NRG location =*******************
NRG_KEY=x
}
Message Id=10011
END OF REPORT
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