You do undef $/, but where do you actually read the contents into $_?

Anyway, this works for me: 

#!/usr/bin/perl
use strict;
use warnings;

$_ = do { local $/; <DATA> };

while ( /^(\d+-\d+-\d+(?:(?!\d+-\d+).)*keyword)(?:(?!\d+-\d+).)*?$/smg
+ ) {
      print "$1\n";
}

__DATA__
2008-10-01 message 1
2008-10-02 message 2
2008-10-03 multi-line message
         message 3 keyword
2008-10-04 message 4
2008-10-05 multi-line
         blah blah
         message 5 keyword junk
2008-10-06 message 6 blah keyword
2008-10-06 this is message 7

[download]

In reply to Re: matching keyword in multi-line records by moritz
in thread matching keyword in multi-line records by arthur99

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.