In principle, the Regexp::Common module could be the simplest thing out on CPAN: a library of regexps that you request by name.

Yeah, but that it loses a lot of its power, doesn't? Currently, you can use the "balanced" regex with almost any delimiters you want. If all you could do was to request them by name, you'd need a thousand names to get balanced patterns with a thousand different delimiters, and if you would have the thousand-and-one delimiter, you're out of luck. What you want isn't much different from wanting subroutines that do not take arguments.

Instead it has this crazy interface that looks like hashes of hashes but isn't (the order of the keys doesn't matter),

The order partially matters. It matters for the part that defines the name, but it doesn't matter for the configuration. That's not uncommon for other APIs, where the order of the options doesn't matter, but it does matter for mandatory arguments.

and there's something strange about what it returns that I couldn't be bothered to figure out myself.

It returns an overloaded object. Which stringifies to a pattern.

As for the use re 'eval', there's no way around it if you want to stick to pre 5.10. To do recursion in 5.8.x (or earlier), you need the (??{ }) construct. Which you can use without problems if it appears literally. But will trigger an exception if you interpolate it (the reason being that up to the point (?{ }) and (??{ }) where introduced, interpolating variables in a regex was "safe", it couldn't run Perl code. With the new constructs what was no longer true, so to protect older code, you had to use use re 'eval' if your interpolated variables contain such constructs).

Now, if you don't trust the patterns from Regexp::Common, you shouldn't run them at all, because they will contain (??{ }) and (?{ }) constructs, and will execute Perl code when evaluating a pattern. Regardless whether you set use re 'eval' or not. You need use re 'eval' if you're going to interpolate pattern in a larger regexp, because Perl will first stringify the pattern (except in some trivial cases), and then, if they contain (??{ }) or (?{ }), you need the use re 'eval' or trip the safety mechanism.

In reply to Re^3: Regexp::Common not so common? by JavaFan
in thread Regexp::Common not so common? by iaw4

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.