while (1) {
    warn "Waiting for PDU";
    $pdu = $smpp->read_pdu() or die "$$: PDU not read. Closing connection";
    print "Received #$pdu->{seq} $pdu->{cmd}:". Net::SMPP::pdu_tab->{$pdu->{cmd}}{cmd} ."\n"
	;
    warn Dumper($pdu) if $trace;

    if (defined reply_tab->{$pdu->{cmd}}) {
	&{reply_tab->{$pdu->{cmd}}{reply}}($c, $pdu);
	warn "Replied";
    } else {
	warn "Don't know to reply to $pdu->{cmd}";
	sleep 1;
    }
}


##</code><code>##

0x00000015 => { cmd => 'enquire_link',
		    reply => sub { my ($me, $pdu) = @_;
				   $me->enquire_link_resp(seq => $pdu->{seq}) }, },

##</code><code>##

Received #2 21:enquire_link
$VAR1 = bless( {
                 'known_pdu' => 1,
                 'cmd' => 21,
                 'status' => 0,
                 'data' => '',
                 'reserved' => undef,
                 'seq' => 2
               }, 'Net::SMPP::PDU' );
Can't call method "enquire_link_resp" on an undefined value at .....esme-re.pl line 89.