In case it helps to see a working example, here's a stripped down version of your code configured to work with my universities public ldap server: 
use strict;
use warnings;
use Net::LDAP;
use Net::LDAP::Util qw(ldap_explode_dn);

my $ldap = Net::LDAP->new("ldap.sfu.ca:1389") or die $!;
my $bind = $ldap->bind();
my @attr = (qw(sn givenName cn mail));
my @args = (    base =>  'ou=people,o=SFU,c=CA',
                scope => 'sub',
                filter =>  '(objectclass=*)',
                attrs => \@attr);

$,=',';
my $mesg = $ldap->search ( @args ) or die $!;
while (my $entry = $mesg->shift_entry()) {
        my $UID = ldap_explode_dn($entry->dn())->[0]->{UID};
        print $UID, (map {$entry->get_value($_)} @attr), "\n";
}

[download]

In reply to Re: Perl LDAP script error "Can't call method "dn" on an undefined value" by Loops
in thread Perl LDAP script error "Can't call method "dn" on an undefined value" by anakin30

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