I was actually surprised, because this code was the first code in Obfuscation that I *did* understand just by looking at it (hmmm... My Perl knowledge must be progressing ;)

This is taken from perlmod manpage:

The old package delimiter was a single quote, but double
 colon is now the preferred delimiter, in part because it's 
more readable to humans, and in part because it's more 
readable to emacs macros. It also makes C++ programmers feel
 like they know what's going on--as opposed to using the 
single quote as separator, which was there to make Ada 
programmers feel like they knew what's going on. Because the 
old-fashioned syntax is still supported for backwards 
compatibility, if you try to use a string like "This is 
$owner's house", you'll be accessing $owner::s; that is, the 
$s variable in package owner, which is probably not what you 
meant. Use braces to disambiguate, as in "This is ${owner}'s 
house".