为什么我从XML::SAX::purePerl::encodingdetect中得到错误,尽管我没有加载该模块?

下面是我为更改位于不同位置的XML文件中某个参数的值而编写的脚本:

#!/usr/bin/perl -w

use Cwd;
use XML::Simple;
use Data::Dumper;
no warnings;

my $before_upgrade_value = &pre_upgrade_value;
print "Value before upgrade:: $before_upgrade_value \n";

&change_value ($before_upgrade_value);

&change_value ("America");

my $after_upgrade_value = &pre_upgrade_value;

print "Value after upgrade:: $after_upgrade_value \n";
print "Done \n";

sub pre_upgrade_value {
    my $xml = new XML::Simple;

    # read XML file
    my $input_xml  = "/usr/tmp/country/CountryConfig.xml";

    my $data = $xml->XMLin($input_xml);
    my $arg0 = $data->{COMMON}->{COUNTRY_LIST}->{Value};

    print "Arg0 is $arg0 \n";
    return $arg0;
}

sub change_value {
    my $arg0 = shift;

    my $arg1 = "ENGLAND";

    my $arg2 = "/usr/tmp/country/CountryConfig.xml";

    system("perl -pi -e 's/$arg0/$arg1/' $arg2");
}

但我得到了以下错误:

无法在/usr/local/lib/perl5/site_perl/5.8.7/xml/sax/pureperl/encodingdetect.pm行100识别此文档的编码。文档需要元素[ln:1,col:0]

你能告诉我为什么我不在我的代码中调用encodingdetect.pm吗?