"I should have been clearer, ..."

No, you were clear enough; I should have been more thorough in my reading of your question. Anyway, I've already picked up on that and updated my response.

Here's how you'd go about using a variable domain name in Perl; I'll leave you to figure out how to implement that in Privoxy. Note: I've added a few more tests. 

#!/usr/bin/env perl

use strict;
use warnings;

my $html_fragment = <<'END_HTML';
    <img src="http://images.google.com/someimage.jpg" />
    <img src="http://images.google.com/NOTsomeimage.jpg" />
    <img src="http://google.somesite.org/image.jpg" />
    <img src="http://somesite.net/google/image.jpg" />
    <img src="http://anythingelse.com/etc.jpg" />
    <img src="http://pictures.google.com/someimage.jpg" />
    <img src="http://google.com/someimage.jpg" />
END_HTML

my $domain_to_keep = 'google.com';

print "Initial markup:\n";
print $html_fragment;

$html_fragment =~ s/\s*<img.*src="http:\/\/(?!.*\Q$domain_to_keep\E\/)
+[^>]+>//gm;

print "Modified markup:\n";
print $html_fragment;

[download]

Output:

Initial markup:
    <img src="http://images.google.com/someimage.jpg" />
    <img src="http://images.google.com/NOTsomeimage.jpg" />
    <img src="http://google.somesite.org/image.jpg" />
    <img src="http://somesite.net/google/image.jpg" />
    <img src="http://anythingelse.com/etc.jpg" />
    <img src="http://pictures.google.com/someimage.jpg" />
    <img src="http://google.com/someimage.jpg" />
Modified markup:
    <img src="http://images.google.com/someimage.jpg" />
    <img src="http://images.google.com/NOTsomeimage.jpg" />
    <img src="http://pictures.google.com/someimage.jpg" />
    <img src="http://google.com/someimage.jpg" />

[download]

-- Ken

In reply to Re^3: GREP Question: Filtering out third-party images with Privoxy by kcott
in thread GREP Question: Filtering out third-party images with Privoxy by karld12

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.