graff has answered your question. fwiw I find HTML::TokeParser::Simple can, imo, help make this sort of task easier. 
#!/usr/bin/perl

use strict;
use warnings;

use HTML::TokeParser::Simple;

my $sample_HTML = <<EOD;
<HTML>
blah.
<CDATA> 
Just some random whatever. It might have some <b>real</b> HTML like a 
+table or CSS styling

or even some <H1>IMPORTANT</H1> words. Maybe even a form <form method=
+post>...</form> 
</CDATA>
</HTML>
EOD

my $p = HTML::TokeParser::Simple->new(\$sample_HTML)
  or die qq{parse failed\n};
  
my ($in_cdata, $cdata);
while (my $t = $p->get_token){
  $in_cdata++, next if $t->is_start_tag(q{cdata});
  $in_cdata--, next if $t->is_end_tag(q{cdata});  
  next unless $in_cdata;
  $cdata .= $t->as_is;
}

print $cdata;

[download]
 
Just some random whatever. It might have some <b>real</b> HTML like a 
+table or CSS styling

or even some <H1>IMPORTANT</H1> words. Maybe even a form <form method=
+post>...</form>

[download]

In reply to Re: HTML::TokeParser Frustration by wfsp
in thread HTML::TokeParser Frustration 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.