Perl 5.22以后的语法更新：Unescaped left brace in regex is illegal here in regex; marked by

虚拟主机的操作系统升级后，perl的版本也升级到了5.26.x，awstats的统计中断了，从后台的错误信息：

Unescaped left brace in regex is illegal here in regex; marked by

查了一下，此类信息应该是从5.22开始的：
As written by @Leobaillard you can use his patch. If you want to fix this with your editor (vi) you can go to line 3936 and make the following changes
$ vi buildroot/output/host/usr/bin/automake
goto line :3936 and change
$text =~ s/\${([^ \t=:+{}]+)}/substitute_ac_subst_variables_worker ($1)/ge;
to
$text =~ s/\$\{([^ \t=:+\{\}]+)\}/substitute_ac_subst_variables_worker ($1)/ge;
The error is with automake and perl v5.26.

从perl v5.22开始：不再推荐在正则表达式中使用 {，而且如果没有转义 \{ 会有错误警告，从v5.26开始：不仅有警告，还会有语法错误提示。

解决方法：在所有正则表达式的 "{" "}" 前面增加转义符:

diff -r1.1008 awstats.pl
9045,9050c9045,9050
< $LogFormatString =~ s/\"%{Referer}i\"/%refererquot/g;
< $LogFormatString =~ s/\"%{User-Agent}i\"/%uaquot/g;
< $LogFormatString =~ s/%{mod_gzip_input_size}n/%gzipin/g;
< $LogFormatString =~ s/%{mod_gzip_output_size}n/%gzipout/g;
< $LogFormatString =~ s/%{mod_gzip_compression_ratio}n/%gzipratio/g;
< $LogFormatString =~ s/\(%{ratio}n\)/%deflateratio/g;
---
> $LogFormatString =~ s/\"%\{Referer\}i\"/%refererquot/g;
> $LogFormatString =~ s/\"%\{User-Agent\}i\"/%uaquot/g;
> $LogFormatString =~ s/%\{mod_gzip_input_size\}n/%gzipin/g;
> $LogFormatString =~ s/%\{mod_gzip_output_size\}n/%gzipout/g;
> $LogFormatString =~ s/%\{mod_gzip_compression_ratio\}n/%gzipratio/g;
> $LogFormatString =~ s/\(%\{ratio\}n\)/%deflateratio/g;