Ummm...I just checked the source of the one that's already on the site vs what you have. Here's what I see. First, the official version:

# Search file for cpan.org
#
# Creation:  2000 by Binary Runner  <binary_runner@rocketmail.com>
# Updated: 2003-02-26 by Paul Millar

<SEARCH
    version = "7.1"
    name = "cpan.org"
    method = "get"
    action = "http://search.cpan.org/search"
    description = "CPAN Search"
    searchform = "http://search.cpan.org/"

>

<input name="query" user>
<input name="mode"  value="all">
<input name="n" value="20">
<input name="sourceid" value="mozilla-search">

<interpret
    browserResultType = "result"
    resultListStart = "<br><div class=t4>"
    resultListEnd = "<center> <b>1</b> &middot;"
    resultItemStart = "  <p><a "
    resultItemEnd = "<br /><small>"
>

</search>

<BROWSER
      update="http://mycroft.mozdev.org/plugins/cpan.src"
      updateIcon="http://mycroft.mozdev.org/plugins/cpan.gif"
      updateCheckDays="3"
>
[download]

Next, the one I downloaded from your site:

<search
 version="7.1"
 name="search CPAN.org"
 description="search CPAN.org"
 action="http://search.cpan.org/search"
 searchForm="http://search.cpan.org"
 method="GET" >

<input name="sourceid" value="Mozilla-search">
<input name="query" user>

<interpret
 resultListStart="<!-- RESULT LIST START -->"
 resultListEnd="<!-- RESULT LIST END -->"
 resultItemStart="<!-- RESULT ITEM START -->"
 resultItemEnd="<!-- RESULT ITEM END -->"
>
</search>

<browser
 update="http://mycroft.mozdev.org/plugins/cpan.src"
 updateIcon="http://mycroft.mozdev.org/plugins/cpan.gif"
 updateCheckDays="3"
>
[download]

Now, I'm not an expert at Mozilla search plugins, but those look awefully similar...down to the version number even.