LWP post cannot get result page. LWP post did not send correct form data.

[Gary Yang]

I have been trying to learn LWP Post, by going through an examples on the web. 
Perl & LWP. I try to search AbeBooks for the book "Codex Seraphinianus" from 
the main page (AbeBooks). Below is the code that I am using. But this just 
sends me back the content of the search page not the result page. Anyone knows 
what the problems are? Can someone show me a real working code of LWP post? 

Here is the code that I am using:

#!/usr/bin/perl -w

use strict;
use LWP;

my $browser = LWP::UserAgent->new;

my $response = $browser->post('http://www.abebooks.com',
   ["sts" => "t", 
    "an" => "", 
    "tn" => "Codex Seraphinianus",
    "kn" => "",
    "isbn" => "",
   ]
);

die "Error: ", $response->status_line, "\n" unless $response->is_success;

my $out_file = "result_seraph.html"; # where to save it
open(OUT, ">$out_file") || die "Can't write-open $out_file: $!";

binmode(OUT);
print OUT $response->content;
close(OUT);
print "Bytes saved: ", -s $out_file, " in $out_file\n";


 Below are the related html code from abebooks.com. 


<form action="/servlet/SearchResults" method="post" name="homepageSearch">
<table cellpadding="3" cellspacing="0" width="100%" border="0">
            <tr>
              <td class="attributeHeader" align="right">Author:</td>
              <td width="74%" align="left">
              <input type="hidden" name="sts" value="t" />
              <input type="text" name="an" size="40" tabindex="10" 
title="Author Field: Enter the name of the author you are searching for 
here"></td>
              </tr>
            <tr>
              <td class="attributeHeader" align="right">Title:</td>
              <td align="left"><input type="text" name="tn" size="40" 
tabindex="11" title="Title Field: Enter the title of the book you are searching 
for here"></td>
            </tr>
            <tr>
              <td class="attributeHeader" align="right">Keyword:</td>
              <td align="left"><input type="text" name="kn" size="40" 
tabindex="12" title="Keyword Field: Enter keywords related to the book you are 
searching for here (eg. Horror, Spanish Language)"></td>
            </tr>
            <tr>
              <td class="attributeHeader" align="right"><span class="tip"><a 
href="/docs/what-is-an-isbn/" 
onclick="window.open(this.href,'ISBN','height=400,width=380,location=no,toolbar=no,scrollbars=yes,resizable=yes');
 return false">what's this?</a></span> ISBN:</td>
              <td align="left"><input type="text" name="isbn" size="40" 
tabindex="13" title="ISBN Field: Enter the ISBN of the book you are searching 
for here"></td>
            </tr>
                        <tr>
                            <td>&nbsp;</td>
              <td class="button" align="left">
                <input type="image" src="/images/Shared/findBook-large.gif" 
alt="FIND BOOK" tabindex="14" >
                &nbsp;
                <a href="/servlet/SearchEntry" tabindex="15" title="More Search 
Options">More Search Options</a>              </td>
                        </tr>
                </table></form>