为什么我在mod_perl下使用“use constant”获得“重新定义”警告

[Thu Jul 30 09:39:37 2009] upload.pl: Constant subroutine ModPerl::ROOT::ModPerl::Registry::home_stanislav_cgi_perl_upload_2epl::UPLOAD_DIR redefined at /usr/share/perl/5.10/constant.pm line 115,line 133.
Constant subroutine
    ModPerl::ROOT::ModPerl::Registry::home_stanislav_cgi_perl_upload_2epl::BUFFER_SIZE redefined at /usr/share/perl/5.10/constant.pm line 115,line 133 (#1)
[Thu Jul 30 09:39:37 2009] upload.pl: Constant subroutine ModPerl::ROOT::ModPerl::Registry::home_stanislav_cgi_perl_upload_2epl::BUFFER_SIZE redefined at /usr/share/perl/5.10/constant.pm line 115,line 133.
Constant subroutine
    ModPerl::ROOT::ModPerl::Registry::home_stanislav_cgi_perl_upload_2epl::MAX_FILE_SIZE redefined at /usr/share/perl/5.10/constant.pm line 115,line 133 (#1)
[Thu Jul 30 09:39:37 2009] upload.pl: Constant subroutine ModPerl::ROOT::ModPerl::Registry::home_stanislav_cgi_perl_upload_2epl::MAX_FILE_SIZE redefined at /usr/share/perl/5.10/constant.pm line 115,line 133.
Constant subroutine
    ModPerl::ROOT::ModPerl::Registry::home_stanislav_cgi_perl_upload_2epl::MAX_DIR_SIZE redefined at /usr/share/perl/5.10/constant.pm line 115,line 133 (#1)
[Thu Jul 30 09:39:37 2009] upload.pl: Constant subroutine ModPerl::ROOT::ModPerl::Registry::home_stanislav_cgi_perl_upload_2epl::MAX_DIR_SIZE redefined at /usr/share/perl/5.10/constant.pm line 115,line 133.
Constant subroutine
    ModPerl::ROOT::ModPerl::Registry::home_stanislav_cgi_perl_upload_2epl::MAX_OPEN_TRIES redefined at /usr/share/perl/5.10/constant.pm line 115,line 133 (#1)
[Thu Jul 30 09:39:37 2009] upload.pl: Constant subroutine ModPerl::ROOT::ModPerl::Registry::home_stanislav_cgi_perl_upload_2epl::MAX_OPEN_TRIES redefined at /usr/share/perl/5.10/constant.pm line 115,line 133.
Subroutine dir_size redefined at /home/stanislav/cgi/perl/upload.pl line 79,line 133 (#2)
[Thu Jul 30 09:39:37 2009] upload.pl: Subroutine dir_size redefined at /home/stanislav/cgi/perl/upload.pl line 79,line 133.
Subroutine error redefined at /home/stanislav/cgi/perl/upload.pl line 90,line 133 (#2)
[Thu Jul 30 09:39:37 2009] upload.pl: Subroutine error redefined at /home/stanislav/cgi/perl/upload.pl line 90,line 133.
Argument "" isn't numeric in numeric ge (>=) at
    /home/stanislav/cgi/perl/upload.pl line 62 (#4)
[Thu Jul 30 09:39:37 2009] -e: Argument "" isn't numeric in numeric ge (>=) at /home/stanislav/cgi/perl/upload.pl line 62.
Filehandle OUTPUT opened only for input at /home/stanislav/cgi/perl/upload.pl
    line 69 (#5)
[Thu Jul 30 09:39:37 2009] -e: Filehandle OUTPUT opened only for input at /home/stanislav/cgi/perl/upload.pl line 69.
Constant subroutine
    ModPerl::ROOT::ModPerl::Registry::home_stanislav_cgi_perl_upload_2epl::UPLOAD_DIR redefined at /usr/share/perl/5.10/constant.pm line 115,line 133 (#1)

为什么这条线路存在并且有办法阻止它们？

发出此警告的代码(摘自“使用Perl进行CGI编程”一书
错误修复)：

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


use CGI;
use CGI::Carp;
#use diagnostics qw/-verbose/;

use Fcntl qw( :DEFAULT :flock );
use constant UPLOAD_DIR     => "/tmp/test_upload/";
use constant BUFFER_SIZE    => 16_384;
use constant MAX_FILE_SIZE  => 1_048_576;       # Limit each upload to 1 MB
use constant MAX_DIR_SIZE   => 100 * 1_048_576; # Limit total uploads to 100 MB
use constant MAX_OPEN_TRIES => 100;

$CGI::DISABLE_UPLOADS   = 0;
$CGI::POST_MAX          = MAX_FILE_SIZE;
my $q = new CGI;
$q->cgi_error and error( $q,"Error transferring file: " . $q->cgi_error );
my $file      = $q->param( "file" )     || error( $q,"No file received." );
my $filename  = $q->param( "filename" ) || error( $q,"No filename entered." );
my $fh        = $q->upload( "file" )     || error( $q,"Something is wrong with file handle." );
#my $fh        = $q->upload( $file );
my $buffer    = "";
if ( dir_size( UPLOAD_DIR ) + $ENV{CONTENT_LENGTH} > MAX_DIR_SIZE ) {
    error( $q,"Upload directory is full." );
}
# Allow letters,digits,periods,underscores,dashes
# Convert anything else to an underscore
$filename =~ s/[^w.-]/_/g;
if ( $filename =~ /^(w[w.-]*)/ ) {
    $filename = $1;
}
else {
    error( $q,"Invalid file name; files must start with a letter or number." );
}
# Open output file,making sure the name is unique
until ( sysopen OUTPUT,UPLOAD_DIR . $filename,O_CREAT | O_EXCL ) {
    $filename =~ s/(d*)(.w+)$/($1||0) + 1 . $2/e;
    $1 >= MAX_OPEN_TRIES and error( $q,"Unable to save your file." );
}
# This is necessary for non-Unix systems; does nothing on Unix
binmode $fh;
binmode OUTPUT;
# Write contents to output file
while ( read( $fh,$buffer,BUFFER_SIZE ) ) {
    print OUTPUT $buffer;
}
close OUTPUT;

if ( -T $fh ) {
    print $q->header("text/plain");
    seek $fh,0;
    map { print } ;
}

sub dir_size {
    my $dir = shift;
    my $dir_size = 0;

    # Loop through files and sum the sizes; doesn't descend down subdirs
    opendir DIR,$dir or die "Unable to open $dir: $!";
    while ( $_ = readdir DIR ) {
        $dir_size += -s "$dir/$_";
    }
    return $dir_size;
}
sub error {
    my( $q,$reason ) = @_;

    print $q->header( "text/html" ),$q->start_html( "Error" ),$q->h1( "Error" ),$q->p( "Your upload was not procesed because the following error ","occured: " ),$q->p( $q->i( $reason ) ),$q->end_html;
    exit;
}

此代码具有类似的输出：
$perl -e’sub FOO(){1} BEGIN {* FOO = sub(){2};打印FOO;’

Constant subroutine main::FOO redefined at -e line 1.

我确实没有发出任何警告qw /重新定义/但它没有帮助.