#!/usr/bin/env perl       
use strict;
use warnings;
use XML::XPath;
use Data::Dumper;

my $xml = 'ApplicationList.xml';
my $xp = XML::XPath->new(filename => $xml);

my %appid = ();
for ($xp->findnodes('/application_list/application/@id') ) {
  my $id = $_->string_value;
  $id =~ s/^\s+|\s+$//g;
  $appid{$id} = 1;;
}
print Dumper \%appid;

my $eventxml = 'events.xml';
my $evenxp = XML::XPath->new(filename => $eventxml);
my $xpath = "//event/custom_attribute_list/custom_attribute[normalize-space(name)='SLB_SSRID']/value";

my @eventrecords = ();
foreach my $node ($evenxp->findnodes($xpath)) { 
  my $ssrid = $node->string_value;
  $ssrid =~ s/^\s+|\s+$//g ;
  if ( exists $appid{$ssrid} ){
    push @eventrecords, 
      { eventid => $ssrid };
  } 
}
print Dumper \@eventrecords;