perl – XML :: Twig keep_encoding如何工作？

它使用XML :: Twig来做到这一点.它创建了没有keep_encoding的XML :: Twig对象($twig = XML :: Twig-> new())但如果我给它一个带有非ASCII字符的UTF-8编码的XML文件,它会生成一个文件根据Ubuntu上的isutf8命令,它不是有效的UTF-8.在xxd中打开文件,我可以看到字符从2字节变为1.

如果我使用我的$twig = XML :: Twig-> new(keep_encoding => 1);相同的输入产生有效的UTF-8并保留两个字节.

根据Perldoc的keep_encoding

This is a (slightly?) evil option: if the XML document is not UTF-8
encoded and you want to keep it that way,then setting keep_encoding
will use theExpat original_string method for character,thus keeping
the original encoding,as well as the original entities in the
strings.

为什么在没有该选项的情况下生成非UTF-8文档,为什么设置它会导致保留UTF-8-ness？

顺便说一下,非ASCII字符是一个不间断的空格(c2 a0).

use strict;
use warnings;
use XML::Twig;
my  $sXML  = join "",(<>);
my  $params = [qw(none nsgmls nice indented record record_c)];
my  $sPrettyFormat  = $params->[3] || 'none';
my $twig = XML::Twig->new();
$twig->set_indent(" "x4);
$twig->parse( $sXML );
$twig->set_pretty_print( $sPrettyFormat );
$sXML      = $twig->sprint;
print $xXML;