this is old and ugly but has been used daily for quite some time. the real version uses another method to get the needed passwords, i've removed that chunk for clarity.

#!/usr/bin/perl
use strict;
use warnings;
$|++;

sub usage { my $n = ($0 =~ s:.*/::, $0); return <<_EOU_;
Usage: $n [-e] [-a] router [cmdfile [outfile [errfile]]]

  -e  -- do enable.
  -a  -- append to outfile and errfile.

  \$ cat >dothis
  sho inter lo0
  sho inter gi3/2
  ^D
  \$ rtrchat -e rtrname dothis
  interface Loopback0
  ....
  \$

_EOU_
}

use Getopt::Std;
my %opt;
getopts('ea',\%opt);

my $rtr = shift @ARGV or die usage;
my $if = shift @ARGV;
my $of = shift @ARGV if $if;
my $ef = shift @ARGV if $of; 

my $console = 'pass';
my $enable  = 'pass';

#print "$rtr $if $of $ef @pw\n";

if ($if) {
  open(IF,"<$if") or die "open $if: $!";
} else {
  *IF = *STDIN;
}

my @ci = <IF>; close(IF);

my $rw = $opt{a} ? '>>' : '>' ;

chomp @ci;

if ($of) {
  open(OF,"$rw$of") or die "open $of: $!";
} else {
  *OF = *STDOUT;
}

if ($ef) {
  open(EF,"$rw$ef") or die "open $ef: $!";
} else {
  *EF = *STDERR;
}

# while (<IF>) { print OF; print EF "foo $_" }

use Net::Telnet::Cisco;

my $c=Net::Telnet::Cisco->new(Host=>$rtr, Timeout => 45)
  or die"connect $rtr: $!";

$c->errmode( sub { print EF @_,"\n" } );

$c->login("nobody",$console) or die "login";

$c->enable($enable) or die "enable" if $opt{e};

$c->cmd("term len 0")or die "len";

foreach (@ci) {
 print OF $c->cmd($_);
}

$c->close;
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