I am not so sure how to include Data::Dumper or print statements into the code.

So I take it you're not a Perl programmer? I would suggest you read perlintro, it's not very long and it'll give you a good idea of Perl's syntax. Then, you can insert use Data::Dumper; above the line use Net::LDAP;, and at various places in the code, insert print Dumper($variable); or print Dumper(\@array); statements to get debug output, which you can compare across the two machines, or post here for feedback, if you like.

Just for example, you might insert print Dumper($mail); inside the loop foreach my $mail ( $entry->get_value( "proxyAddresses" ) ) { ... } to see which, if any, mail addresses you are getting and whether they match the pattern /^(smtp|SMTP):/. You can repeat this for the other loops to see how many times those loops get executed, etc.

Perl version for the successful script is 0.4001 and where it is failing 0.65.

Have you had a chance to investigate poj's suggestion?

My apologies I am not a perl programmer I come from the Linux side. 1. I now have the code as :-

use Data::Dumper;
use Net::LDAP;
use Net::LDAP::Control::Paged;
use Net::LDAP::Constant ( "LDAP_CONTROL_PAGED" );
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. . .

while(1) {
  # Perform search
  my $mesg = $ldap->search( @args );

# Filtering results for proxyAddresses attributes
  foreach my $entry ( $mesg->entries ) {
    my $name = $entry->get_value( "cn" );
    # LDAP Attributes are multi-valued, so we have to print each one.
    foreach my $mail ( $entry->get_value( "proxyAddresses" ) ) {
     # Test if the Line starts with one of the following lines:
     # proxyAddresses: [smtp|SMTP]:
     # and also discard this starting string, so that $mail is only th
+e
     # address without any other characters...
     if ( $mail =~ s/^(smtp|SMTP)://gs ) {
       push(@valid, $mail." OK\n");
       print Dumper($mail);
     }
    }
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I do not get any output

Using Poj's Suggesstion:- I get this error message:- root@vm1000 getadscripts# ./getadsmtp_itbak1.pl Name "main::valid" used only once: possible typo at ./getadsmtp_itbak1.pl line 116, <DATA> line 755. $VAR1 = '/etc/postfix/ad_itdepartment';

I have marked up your code with the 2 lines you need to comment out and 3 lines to add

while(1) {
  # Perform search
  my $mesg = $ldap->search( @args );

  # Filtering results for proxyAddresses attributes
  foreach my $entry ( $mesg->entries ) {
    my $name = $entry->get_value( "cn" );
    # LDAP Attributes are multi-valued, so we have to print each one.
    foreach my $mail ( $entry->get_value( "proxyAddresses" ) ) {
      # Test if the Line starts with one of the following lines:
      # proxyAddresses: [smtp|SMTP]:
      # and also discard this starting string, so that $mail is only t
+he
      # address without any other characters...
      if ( $mail =~ s/^(smtp|SMTP)://gs ) {
         push(@valid, $mail." OK\n");
      }
    }
  }

  # Only continue on LDAP_SUCCESS
  $mesg->code and last;

  # Get cookie from paged control
  my($resp)  = $mesg->control( LDAP_CONTROL_PAGED ) or last;
  
  #$cookie    = $resp->cookie or last;             # delete
  $cookie = $resp->cookie;                         # add
  last if (!defined($cookie) || !length($cookie)); # add

  # Set cookie in paged control
  $page->cookie($cookie);
}

#if ($cookie) {                            # delete
if (defined($cookie) && length($cookie)) { # add

  # We had an abnormal exit, so let the server know we do not want any
+ more
  $page->cookie($cookie);
  $page->size(0);
  $ldap->search( @args );
  # Also would be a good idea to die unhappily and inform OP at this p
+oint
     die("LDAP query unsuccessful");
}
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poj