I have since figured it out. Thank you for your time and replies.

#!/usr/bin/env plackup

use HTTP::Request;
use Data::Dumper;
use WWW::Mechanize;
use strict;
use warnings;
use Plack::Request;
use Facebook::Graph;
use LWP::Simple;

my $app = sub {
       my $env = shift;

my $app_id        = 'xxxxxxxxxxxx';
my $app_secret        = 'xxxxxxxxxxxxxxxxxxxxxxxxxx';
my $postback_url    = 'my postback url';

my $fb = Facebook::Graph->new(

    app_id          => $app_id,
    secret          => $app_secret,
    postback        => "$postback_url/callback",
    );

my $uri = $fb
    ->authorize
    ->extend_permissions(qw(offline_access read_stream publish_stream 
+user_photos))
    ->set_display('page')
    ->uri_as_string;

my $req = Plack::Request->new($env);
$fb->request_access_token($req->query_parameters('code'));

};
[download]

With this

system("/opt/google/chrome/chrome", "$uri");

print "Code = "; 
chomp( my $code = <> );

   my $token_response_object = $fb->request_access_token($code);
   my $token_string = $token_response_object->token;
   my $token_expires_epoch = $token_response_object->expires;
[download]