$has_field2 =~ s/field1:[\n]*\n\K(?!field2:).*(?=\nfield3:)
                /field2: valueB
                /msx;

[download]

  1. Shouldn't the  [\n]*\n after  field1: in the search pattern be  [^\n]*\n (negated class) instead?
  2. The  .* in the search pattern is greedy. Your test string has only one occurrence of the  "field1: valueA\nfield2: valueB\nfield3: valueC\n" substring. What happens if you test against many occurrences (see below — BTW, I have an updated version of this script that, among other things, uses hi-res timing if you're interested)? Won't the greedy  .* just gobble all intervening occurrences?
  3. You have a newline and a lot of blank space in your replacement string; is this what you want? 
    c:\@Work\Perl\monks\Zu>perl -wMstrict -le
"my $s = 'xxxyxxx';
 $s =~ s/y
        /FOO
        /xms;
 print qq{'$s'};
"
'xxxFOO
   xxx'

    [download]

In reply to Re^3: Efficient method to replace middle lines only when no match by AnomalousMonk
in thread Efficient method to replace middle lines only when no match by Zu

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.