I have tired with your code but not getting expected result . My samlple.xml

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<event_list xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmln
+s:xs="http://www.w3.org/2001/XMLSchema" xmlns="http://www.hp.com/2009
+/software/opr/data_model" total_size="34" page_size="20" start_index=
+"1" self="https://testurl/event_list?query=title+LIKE+%22PROBING%2810
+0%29%2425%22" type="urn:x-hp:2009:software:data_model:opr:type:event_
+list" version="1.1">
    <drilldown_url>
https://testurl/opr-web/opr-evt-browser</drilldown_url>
    <event relationships_included="true" self="https://testurl/event_l
+ist/031c3c70-4ace-71e7-0b5b-88fb83170000" type="urn:x-hp:2009:softwar
+e:data_model:opr:type:event" version="1.3">
        
        <state>
open</state>
        <severity>
critical</severity>
        <priority>
medium</priority>
        <category>
SAR_OP_Service</category>
        <application>
business_transaction_group</application>
        <time_created>
2017-06-06T15:37:13Z</time_created>
        <time_changed>
2017-06-20T10:37:20.098Z</time_changed>
        <time_received>
2017-06-20T10:37:20.156Z</time_received>
        <time_first_received>
2017-06-06T15:37:17.414Z</time_first_received>
        <custom_attribute_list self="https://testurl/event_list/031c3c
+70-4ace-71e7-0b5b-88fb83170000/custom_attribute_list" type="urn:x-hp:
+2009:software:data_model:opr:type:event:custom_attribute_list" versio
+n="1.0">
            <custom_attribute self="https://testurl/event_list/031c3c7
+0-4ace-71e7-0b5b-88fb83170000/custom_attribute_list/SAR_RemedyInciden
+t" type="urn:x-hp:2009:software:data_model:opr:type:event:custom_attr
+ibute" version="1.0">
                <name>
SAR_RemedyIncident</name>
                <value>
INC000018745375</value>
            </custom_attribute>
            <custom_attribute self="https://testurl/event_list/031c3c7
+0-4ace-71e7-0b5b-88fb83170000/custom_attribute_list/SAR_RemedyQueue" 
+type="urn:x-hp:2009:software:data_model:opr:type:event:custom_attribu
+te" version="1.0">
                <name>
SAR_RemedyQueue</name>
                <value>
Coll@borate-L3</value>
            </custom_attribute>
            <custom_attribute self="https://testurl/event_list/031c3c7
+0-4ace-71e7-0b5b-88fb83170000/custom_attribute_list/SAR_RemedyStatus"
+ type="urn:x-hp:2009:software:data_model:opr:type:event:custom_attrib
+ute" version="1.0">
                <name>
SAR_RemedyStatus</name>
                <value>
Assigned</value>
            </custom_attribute>
            <custom_attribute self="https://testurl/event_list/031c3c7
+0-4ace-71e7-0b5b-88fb83170000/custom_attribute_list/SAR_SSRID" type="
+urn:x-hp:2009:software:data_model:opr:type:event:custom_attribute" ve
+rsion="1.0">
                <name>
SAR_SSRID</name>
                <value>
957</value>
            </custom_attribute>
            <custom_attribute self="https://testurl/event_list/031c3c7
+0-4ace-71e7-0b5b-88fb83170000/custom_attribute_list/Service%20Name" t
+ype="urn:x-hp:2009:software:data_model:opr:type:event:custom_attribut
+e" version="1.0">
                <name>
Service Name</name>
                <value>
IPT</value>
            </custom_attribute>
        </custom_attribute_list>
    
        <time_created_label>
6/6/2017 03:37:13 PM</time_created_label>
        <time_changed_label>
6/20/2017 10:37:20 AM</time_changed_label>
        <time_received_label>
6/20/2017 10:37:20 AM</time_received_label>
        <time_first_received_label>
6/6/2017 03:37:17 PM</time_first_received_label>
    </event>
</event_list>
[download]

Suggested code @haukex

#!/usr/bin/perl                        
use warnings;
use strict;

use XML::XPath;
my $file = 'C:/Users/snehit.rahate/Perl/events.xml';
my $xpath = q{//custom_attribute_list/custom_attribute[name='Service N
+ame']/value}; # return no result
my $xp = XML::XPath->new(filename=>$file);
my $nodeset = $xp->find($xpath);
for my $node ($nodeset->get_nodelist) {
    print " XML::XPath: ",$node->string_value,"\n";
}
[download]

I want to concatenate service name and slb_ssrid into one value $appname as shown in below.xml .But not able to fetch the value of tag <name> Service Name</name> my $appname = IPT(957) Please suggest and correct me i am wrong. Thanks a Ton !