#!/usr/bin/perl -w
use strict;
               
my @csv_order = qw ( exchangeIdentity 
                     callIdentificationNumber); 
my %defaults = map {$_ => ""}@csv_order;
                
my %curr_record=%defaults;

while (<DATA>)
{
    if (/CME20CP6.CallDataRecord/.../^\s*$/)
    {
       if ( my ($var,$val) = ($_ =~ m/^\s*(\S+)\s+:\s+(\S+)\s*$/) )
       {  
          $curr_record{$var}=$val if exists ($curr_record{$var}); 
       }
       if (/^\s*$/) #remember to add a blank line at end of file
       {
         dump_csv_line();
         %curr_record=%defaults;
       }
    }
}

sub dump_csv_line
{
   print join (",",map{$curr_record{$_}}@csv_order)."\n";
}

__END__

Prints:
"DWLCCN6",'6CBFD7'H
"DWLCCN6",'6CC99C'H
,'699999'H

__DATA__
CME20CP6.CallDataRecord.uMTSGSMPLMNCallDataRecord
callIdentificationNumber : '6CBFD7'H
exchangeIdentity : "DWLCCN6"
gSMCallReferenceNumber : '9103770001'H
switchIdentity : '0001'H
recordSequenceNumber : '39D42E'H
date : '1409071F'H
serviceFeatureCode : '0002'H
timeForEvent : '131A01'H

CME20CP6.CallDataRecord.uMTSGSMPLMNCallDataRecord
callIdentificationNumber : '6CC99C'H
exchangeIdentity : "DWLCCN6"
switchIdentity : '0001'H
recordSequenceNumber : '39D42F'H
date : '1409071F'H
serviceFeatureCode : '0002'H
timeForEvent : '131A20'H

CME20CP6.CallDataRecord.uMTSGSMPLMNCallDataRecord
callIdentificationNumber : '699999'H