regex - Perl 条件替换

Question

我有一个带占位符的路径名，我想替换它:

# an example path with a placeholder
my $path = '%myproject%Web/ui/images/';

# mapping of all placeholders   
my %placeholders = (
  myproject => 'myproject/installation/all'
);

# substituting all placeholders in the path
$path =~ s!%(.*?)%!/$placeholders{$1}/!g;

# works fine -> 'myproject/installation/all/Web/ui/images/'
print $path; 

这段代码工作正常，但有一个问题:我有一长串文件名和指定的不同占位符(因此是散列)。现在，为了更加稳健，如果路径中指定的占位符在 %placeholders 映射中不存在，我想抛出一个错误。

有什么办法可以实现吗？

Answer 1

Now for the sake of more robustness I'd like to throw an error if there is a placeholder specified in the path which does not exist in the %placeholders mapping

这可以使用 /e 很容易地完成:

$path =~ s{%([^%]+)%}{
   exists($path{$1})
      ? '/'.$path{$1}.'/'
      : die "Placeholder $1 does not exist"
}ge;

注意:我觉得把.*?换成[^%]+比较好，可以防止错误匹配。