Further to davido's post:
bayareamonk: You say you have Perl 5.10 available (which provides \K), so here's a small simplification: 

c:\@Work\Perl\monks>perl -wMstrict -le
"use Regexp::Common 'net';
 ;;
 my $input = qq{<yoda yoda> <ip-compute-10.10.10.1-internal> <yadda ya
+dda> \n}
           . qq{<more stuff>}
           ;
 print qq{[[$input]] \n};
 ;;
 my $want = qq{<yoda yoda> <ip-compute-10.10.25.18-internal> <yadda ya
+dda> \n}
          . qq{<more stuff>}
          ;
 ;;
 my $replacement_ip = '10.10.25.18';
 ;;
 $input =~ s{ <ip-compute- \K $RE{net}{IPv4} (?= -internal>) }
            {$replacement_ip}xmsg;
 ;;
 print $input eq $want ? 'Success:' : 'Failure:';
 print qq{[[$input]]};
"
[[<yoda yoda> <ip-compute-10.10.10.1-internal> <yadda yadda>
<more stuff>]]

Success:
[[<yoda yoda> <ip-compute-10.10.25.18-internal> <yadda yadda>
<more stuff>]]

[download]

In reply to Re^4: Newbie regular expressions question by AnomalousMonk
in thread Newbie regular expressions question by bayareamonk

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.