In list(), I tested just the form generation code and it doesn't look like it's producing valid HTML.

The code I used was:

#!/usr/bin/perl
use strict;
use warnings;
use CGI;

my $q = CGI->new();
my $output = $q->b("Field1: ") . $q->textfield(-name=>'field1',-size=>
+20) .
    $q->p() .
    $q->b("MP3:") . $q->filefield(-name=>'mymp3', -size=>20) .
    $q->p() .
    $q->b("Field2:") . $q->textarea(-name=>'field2',-rows=>4,-cols=>20
+);

$output = $q->start_multipart_form() .
    $q->hidden(-name=>'rm',-value=>'save_mode') .
    $output .
    $q->br() .
    $q->submit(-label=>'Upload') .
    $q->end_form();

print $output;
exit;

__DATA__
<form method="post" action="/./html.pl" enctype="multipart/form-data">
<input type="hidden" name="rm" value="save_mode"  /><b>Field1: </b><in
+put type="text" name="field1" tabindex="1"  size="20" /><p /><b>MP3:<
+/b><input type="file" name="mymp3" tabindex="2"  size="20" /><p /><b>
+Field2:</b><textarea name="field2" tabindex="3" rows="4" cols="20"></
+textarea><br /><input type="submit" tabindex="4" name=".submit" value
+="Upload" /><div></div>
</form>
[download]

As you can see, there is no closing form tag. (Also, some of the fields are in XHTML rather than HTML, so that could be causing problems as well.) I don't have a full answer at the moment, but Firefox 1.5 might be more strict about valid HTML.