Joost beat me to it!

Here's one way 

#!/bin/perl5

use strict;
use warnings;
use HTML::TokeParser;

my $str = q|<img src=\"test.jpg\"> highlight the word <img src=\"word.
+jpg\">|;

my $tp = HTML::TokeParser->new(\$str)
  or die "Couldn't parse $str: $!";

$tp->unbroken_text(1);
  
my ($html, $start);

while (my $tag = $tp->get_token) {
    
  if ($tag->[0] eq 'T'){
    my $t = $tag->[1];
    $t =~ s|word|<b>WORD</b>|g;
    $html .= $t;
  }
  else{
    $html .= $tag->[4] if $tag->[0] eq 'S';
    $html .= $tag->[1] if $tag->[0] eq 'C';
    $html .= $tag->[2] if $tag->[0] eq 'E';
  }

}

print "$html\n";

__DATA__
---------- Capture Output ----------
> "C:\Perl\bin\perl.exe" parse_str.pl

<img src=\"test.jpg\"> highlight the <b>WORD</b> <img src=\"word.jpg\"
+>

> Terminated with exit code 0.

[download]

In reply to Re: Replacing text NOT in an HTML tag by wfsp
in thread Replacing text NOT in an HTML tag by Anonymous Monk

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.