Beefy Boxes and Bandwidth Generously Provided by pair Networks DiBona
Do you know where your variables are?
 
PerlMonks  

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??
... excellent exposition!

Thank you very much!

... the empty regex acts as a stand-in for the regex most recently matched (whether the match was successful or not).

In looking for empty pattern documentation (see below), I discovered this is not the case: "If the PATTERN evaluates to the empty string, the last successfully matched regular expression is used instead." (Strange what you can find when you actually read the docs!) Fixed my reply: thanks!

Is this documented anywhere?

The only place I've seen it is in perlop in the Regexp Quote-Like Operators section: the discussion of the  m// operator has a sub-section titled "The empty pattern //" (there's also a brief back-reference to it in the discussion of the  s/// operator).

Are there any typical use cases for employing the empty regex to mean “repeat the regex used in the previous match”?

My vague impression is this is something that evolved early-on as an emulation of shell usage or maybe from a desire for some kind of command line one-liner short-cut facility: saves typing, y'know. Offhand, I can't come up with a compelling example.


In reply to Re^3: matching problem by AnomalousMonk
in thread matching problem by Balaton

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!
  • 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, 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, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • Outside of code tags, you may need to use entities for some characters:
            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.
  • Log In?
    Username:
    Password:

    What's my password?
    Create A New User
    Chatterbox?
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others rifling through the Monastery: (7)
    As of 2014-04-18 06:36 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      April first is:







      Results (462 votes), past polls