Since your 'pack' question has been answered, I will try to answer your last question.

You would be better off letting Apache cache the image in memory for you using the mod_mmap_static module. Using mod_perl for this is a little overkill, and more than likely slower.

I use something like the following:

AliasMatch /(clear|shim|spacer).gif$ /usr/local/apache/htdocs/clear.gi
+f
MMapFile /usr/local/apache/htdocs/clear.gif
[download]

for Apache 2.0 you could look at the mod_mem_cache module. Also have a look at the mod_expires module which allows you to set arbitrary expiry times for your files to take the most advantage of caches and proxies.

In this case I just don't think perl is right hammer for this nail.