Good one! I like the move away from a hex encoding of the JAPH but you soon get back to the dec ASCII code for JAPH. I have thrown in the prints to demonstrate the ease of decoding using prints to see what is going on.

Here is the whitespaced decode.

tachyon

# base string
$a='-40300aa03aa01aa02-4-1-2-40503aa-4aaaaa02a-400ab-4-1-2aa-2aba-404-
+4-1-2a-400-40503-40505a-403ab-4a-4-4a-1';
print "a1:$a\n";
# change base, sub with more 4xxxxx's
$a=~s/b/-4aaa00/g;
print "a2:$a\n";
# change again
$a=~s/a/-3/g;
print "a3:$a\n";
# change again, \ un-necessary
$a=~s/\s//g;
print "a4:$a\n";
# start a big substitution, in fact change to  '.' sep dec ASCII chr
for(0..77){
   $b.='.' unless ($_*2)%3;
   print "$b\n";
   $b.=4 + substr($a,$_*2,2);
   print "$b\n";
}
# here is a one liner to print it out
# just a . split print chr routine
print chr $1 while $b=~/([^.]+)\./g

# this is the rest of the code, which basically 
# generates the short code above then evals it
#$b=~ s/\./),chr(/g;
#$b=~s/^\),/print/;
#$b=~s/0(\d\d)/$1/g;
#eval($b.')');
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Suggestions: use $_ for your string then use s;foo;; to change it (yes this is valid code). Try to avoid $a=...;$a=...;$a=...; as it is easy to brake the lines, and easy to see what gives. Use s/...../...../e so you can put heaps of code into the RHS. Use ; " ' as regex delims. Be original. Have fun. R&D (Rip-off and Duplicate!) This is my personal best so far. It uses lots of stuff to make it poetic as well as obfu. If you decode it that will be a (public) first. Working out why it parses is a good start, I'm not convinced I understand.

################################################################
#                                                              #
#        A Thought on Perl Poetry and the Immortal JAPH        #
#                                                              #
#  I, require strict* and do not require warnings*. My answer  #
#  equals reference you unless answer equals 42. Question: If  #
#  defined, by this paradigm, do you do, the hacker foo?  Now  #
#  join the data (why Fs & Os?), so the space or newline goes  #
#  Character evaluate: Reverse split null, then for each foo:  #
#  You ate foo, but I ate two. Answer -> Join with null, sort  #
#  the spots, and print it join the dots. Go now and exit, do  #
#  not die, else go to question and answer why? JAPH! (c)JADF  #
#                                                              #
################################################################

I, require strict and do(not require warnings); my $answer = \$u 
unless $answer == '42'; Question: if(defined by this_paradigm do
you_do_the_hacker_foo(??)){sub AUTOLOAD{$_=$now=join'the',<DATA>
;y?FO?01?; s.o|the| |\n..goe;s/(.{7})/(chr(eval'($u,$ate)=(0,1);
foreach $foo(reverse split "",$1){$u+=$ate*$foo;$but_I=$ate*=2;}
$$answer'))/eg;$_= join'',sort/(..)/g and print join'',/.(.)/go;
$now and exit, do(not die)}}else{goto Question and $answer;y???}
 __DATA__

OOFFOOOOOFOO      OFOO       OOFFFOOOFFO    FOOO    FFOO    OFFO
FFFOOFOOOFOF    OFFFFOOF     OFFFOOFOOOOO   OFOO    FOFO    FFFF
    FOOO      FOOF    OOFO   FOOO    OFOF   OOOO    FFOF    OOOF
    OFOF      OOFO    FFFO   OFFF    OOOO   OFFO    OOOF    FFFO
    OFFO      FOFOOOFFOFFO   FFFFFOOOFOFF   OOFFFFOOOFFO    FFOO
    OFOF      FOOFFOFOFOFF   FFFOOFFOOFO    FFFFFOOOOFOF    OOOF
    FFOO      OOOF    FFOO   OFOO           FFOO    OFFF    FOOO
FF  OFOO      FOOO    OOOF   FOFO           OOFO    OFFO        
OOFFOFOO      FFFO    FOOO   FOFO           OOFO    FFOO    OOFO
 FFOOOF       OOOO    OFFO   FOOO           OOFF    OFOF
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