Btw, it is probably cleaner to write 
(?:\z(?{ die })|)

[download]
as 
(?(?=\z)(?{ die }))

[download]

It's too bad your Perl segfaults on die from inside a regex.. that doesn't happen for me (5.8.0 Linux nothreads).

Your troubles with using a lexical are possibly due to these code blocks inside regexes being closures; were you aware of that?

Unfortunately, there is currently no way to tell the regex engine to fail the entire match immediately, which is why die is necessary. It will work in Perl6, but then, so will matching on streams.. :)

The only solution is to do what we did in the days of Pascal to cope with the lack of last and friends: nest conditionals. In terms of the pattern matching, that means an attempt to match

.*?abc(def)?

[download]
becomes something like 
(?(?!\z)
    .*?
    (?(?!\z)
        abc
        (?(?!\z)
            (def)?
            |
            (?{ $PREMATURE_INPUT_END++ })
        )
        |
        (?{ $PREMATURE_INPUT_END++ })
    )
    |
    (?{ $PREMATURE_INPUT_END++ })
)

[download]

Makeshifts last the longest.

In reply to Re^3: Regexes on Streams - Revisited! by Aristotle
in thread Regexes on Streams - Revisited! by tsee

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.