$_="this super-code example shows clearly how encoded text is,
siince a normal perl-codeblock should never-ever-ever contain it's
method embedded within -its- decoder as is. right, you're wrong
because my obstuf exempleifies it. honest programs should a) envoke
and b-work prescripted though never through it.";

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Each word's length is how he encodes "just another perl hacker". Sometimes he mis-spells the words to get the right length: for example siince.
=cut

my@a=map{(/\.|,/)?0:length}(m;([-\w']+|(?:,|\.));g);

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the regex matches each word, so each word is passed to map. Periods and commas return 0, which is the null character, thus not taking up any space.  He does this so he can punctuate his string.  As I said earlier, the length of each word is returned.
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print chr hex sprintf('%x'x2,$$,shift@a)while($$=shift@a);

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Here he goes through @a by twos, performing
sprintf ('%x%x',$$, shift @a)
each time through.  The result is a hexadecimal number for each word, formed by the word's length.  Then he uses hex to turn that hex number into decimal, and chr to turn it into it's ascii equivalent. 
=cut