The idea behind this is that you typically already have images on your web page; so you replace the SRC of one of the images with a URL that routes through this logger, but still returns the image. So the browser doesn't know the difference, but the server does.

So what you should actually do is just use one of the images you already have on your site. You say that the image you want to use is at /home/username/www/cgi-bin/showpic/spacer.gif? That's not right. "showpic" is the name of the CGI script, so it can't also be a directory on the filesystem.

Let's say that you currently have an image like this on your web page:

<img src="/images/foo.gif">
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And the actual filesystem location of this image is:

/home/bar/www/images/foo.gif
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You would replace the IMG tag with this:

<img src="/cgi-bin/showpic/images/foo.gif">
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And, in showpic (the CGI script), you'd set the $home variable to:

my $home = "/home/bar/www";
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Make sense?