CountZero's solution is of course far more elegant. I thought I'd see if I could code a filter using just regex, however:

use strict;
use warnings;

my ($xml, $content, @xml);

$xml = join '', <DATA>;

while ($xml =~ m/(<details>.*?<\/details>)/sg) {
    $content = $1;
    next if $content !~ /<address>.+?<\/address>/;
    push @xml, $content;
}

$xml = "<specification>\n" .
join("\n", map { "  $_" } @xml) .
"\n</specification>";

print $xml;

__DATA__
<specification>
  <details>
    <name>johan</name>
    <address>Langgt 23</address>
    ---more info---
  </details>
  <details>
    <name>venu</name>
    <address>storgatan 27</address>
    ---more info---
  </details>
  <details>
    <name>kent</name>
    <address>nygatan 46</address>
    ---more info----
  </details>
  <details>
    <name>johan</name>
    <branch>ece</branch>
    ---more info--
  </details>
</specification>

[download]

In reply to Re: help need when processing xml using perl by TJPride
in thread help need when processing xml using perl by veerubiji

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.