较新版本的 Perl 上的正则表达式匹配问题

Question

我已经转移到一个新的服务器，使用 Perl 5.22.1。我有这段代码:

$html =~ m{
    ( # $1 the whole tag
        <
        (
            ?:
            !--
            ( # $2 the attributes are all the data between
                .*?
            )
            --
            | # or
            (
                ?:
                ( # $3 the name of the tag
                    /?\S+?\b
                )
                ( # $4 the attributes
                    [^'">]*
                    (
                        ?:
                        ( # $5 just to match quotes
                            ['"]
                        )
                        .*?\5
                        [^'">]*
                    )*
                )
            )
        )
        >
    )
}gsx

...现在它给了我这个错误:

A fatal error has occurred:

    In '(?...)', the '(' and '?' must be adjacent in regex; marked by <-- HERE in m/
                ( # $1 the whole tag
                    <
                    (
                        ? <-- HERE :
                        !--
                        ( # $2 the attributes are all the data between
                            .*?
                        )
                        --
                        | # or
                        (
                            ?:
                            ( # $3 the name of the tag
                                /?\S+?\b
                            )
                            ( # $4 the attributes
                                [^'">]*
                                (
                                    ?:
                                    ( # $5 just to match quotes
                                        ['"]
                                    )
                                    .*?\5
                                    [^'">]*
                                )*
                            )
                        )
                    )
                    >
                )
            / at ./admin/GT/HTML/Parser.pm line 207.
    Compilation failed in require at (eval 25) line 8.

Please enable debugging in setup for more details.

我不太确定它在提示什么。有什么想法吗？

Answer 1

您需要确保 ?:(非捕获组标记)紧跟在左括号之后 即使 x 使用修饰符。

查看固定的正则表达式声明:

$html =~ m{
    ( # $1 the whole tag
        <
        (?:
            !--
            ( # $2 the attributes are all the data between
                .*?
            )
            --
            | # or
            (?:
                ( # $3 the name of the tag
                    /?\S+?\b
                )
                ( # $4 the attributes
                    [^'">]*
                    (?:
                        ( # $5 just to match quotes
                            ['"]
                        )
                        .*?\5
                        [^'">]*
                    )*
                )
            )
        )
        >
    )
}gsx

参见 this reference :

Note that anything inside a \Q...\E stays unaffected by /x. And note that /x doesn't affect space interpretation within a single multi-character construct. For example in \x{...}, regardless of the /x modifier, there can be no spaces. Same for a quantifier such as {3} or {5,}. Similarly, (?:...) can't have a space between the "{" , "?" , and ":". Within any delimiters for such a construct, allowed spaces are not affected by /x, and depend on the construct. For example, \x{...} can't have spaces because hexadecimal numbers don't have spaces in them.

我认为有一个错字 - { 实际上必须是 (。我将与当前场景相关的文本部分加粗了。