getlines from Net::Telnet works different (works/does not work). while loop opt?

[p1qb0d]

Hello.

I'm trying to work with Cisco hardware.

Simple script read the config:

#!/usr/bin/perl

use strict;
use warnings;
use Net::Telnet;

my $t;
my $host = "megahw";
my $username = "megauser";
my $passwd = "megapassword";
my @lines = ();
my $fh;
my $fn = "/var/tmp/t.log";
my $lline;
my @llines = ();
my $ownline;
my $screenlines;

$t = new Net::Telnet(Timeout => 10, Prompt => '/Username: $/');
$t->open($host);
$fh = $t->input_log($fn);
$t->login(Name => $username, Password => $passwd, Prompt => '/#$/');
$t->print("show running-config");
@lines = ();
$ownline = 1;
$screenlines = 25;

while (1){
	@llines = $t->getlines(All => 0);
	$lline = scalar @llines;

	if ($lline == $screenlines){

		while (scalar @llines){
			$lline = shift @llines;
			push @lines, $lline;
		}

		if ($ownline){
			$ownline = 0;
			$screenlines -= 2;
		}

		$t->put(' ');
		next;
	}else{

		while (scalar @llines){
			$lline = shift @llines;
			push @lines, $lline;
		}

		last;
	}

}

$t->print("exit");
$t->break;
$t->close;

while (scalar @lines){
	$lline = shift @lines;
	print $lline;
}

If I run it flat (script.pl) I get my own command only. t.log has:

User Access Verification

Username: megauser
Password: 

megahw#show running-config

If I run it via perl -d script.pl and type c(ontinue) immediately the t.log is the same.

If I run it via perl -d script.pl and go inside while(1) loop via n(ext) commands and then c(continue), the t.log has:

User Access Verification

Username: megauser
Password: 

megahw#show running-config
Building configuration...

Current configuration : 2201 bytes
!
! No configuration change since last restart
!
version 15.2
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
!
hostname megahw
!
boot-start-marker
!
There are many lines of config
!
end

That behaviour is very strange for me.

Any clues?