http://www.perlmonks.org?node_id=420483

A simple play with numbers, and function calls.

My first intentions were different, but I had trouble with big numbers not fitting inside Integer, so this will do for now.

A(split//, join'', map {qq|$_@{[ord(A)+(map-100+ord,split//,
'mdsk')[$.++]]}3|}map{344+((1,-1,-1,1)[$o++]*ord( 'd')*($i++
==3?5:1))+ord}split//,'Codz');sub A{$_[0]&&do{($_[0]!=$_[1])
&&shift and&A||do{shift;shift;$_=$|; {$_*=10;$_+=shift;$_[0]
==3||redo}print chr,chr(1+15*shift);&A;}}}s,,$i++*$o+ord,ex;

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Re: untitled obfu
by jdalbec (Deacon) on Jan 08, 2005 at 16:48 UTC 
    # Analysis phase 1
      print join ' ', map {
        344 + ( ( 1, -1, -1, 1 )[ $o++ ] * ord('d') * ( $i++ == 3 ? 5 
+: 1 ) ) +
# ord('d') == 100 doesn't affect last two digits
          ord
      } split //,
    'Codz';
# 'C' -> 11, 'N' -> 22, 'Y' -> 33, 'd' -> 44, 'o' -> 55, 'z' -> 66,
# '!' -> 77, ',' -> 88, '7' -> 99, '8' -> 00 (if > 0)
# '-' -> 11, '"' -> 22, '{' -> 33, 'p' -> 44, 'e' -> 55, 'Z' -> 66,
# 'O' -> 77, 'D' -> 88, '9' -> 99, '8' -> 00 (if < 0 - doesn't happen 
+here)
print "\n"; undef $o; undef $i; # clean up
# 511 355 344 966
#  ^^  ^^  ^^  ^^ last two digits ==, first digit != second
# could have more digits as long as only last pair == e.g. -1211

# Analysis phase 2
    print join ' ', map {
        qq|$_@{[ord(A)+(map-100+ord,split//,
'mdsk')[$.++]]}3|
# 100 == ord('d') so 'd' -> 'A'
# mdsk -> lcrj -> kbqi -> JAPH (another Caesar cipher!)
      } map {
        344 + ( ( 1, -1, -1, 1 )[ $o++ ] * ord('d') * ( $i++ == 3 ? 5 
+: 1 ) ) +
          ord
      } split //,
    'Codz';
print "\n"; undef $o; undef $i; undef $.; # clean up
# 511743 355653 344803 966723
# ^^^    ^^^    ^^^    ^^^    first 3 digits same as above
#    ^^     ^^     ^^     ^^  JAPH
#      ^      ^      ^      ^ last digit == 3

# Analysis phase 3 (++perltidy!)
A(
    split //,
    join '',
    map {
        qq|$_@{[ord(A)+(map-100+ord,split//,
'mdsk')[$.++]]}3|
      } map {
        344 + ( ( 1, -1, -1, 1 )[ $o++ ] * ord('d') * ( $i++ == 3 ? 5 
+: 1 ) ) +
          ord
      } split //,
    'Codz'
);

# The argument list of A is actually
# split / */, '511743 355653 344803 966723'
# but since A restarts after each number
# (the final 3 is a "stop digit")
# I'll keep them separate in the comments below.
# The stop digit had to be 1, 3, or 9
# since 0, 2, 4, 5, 6, 7, and 8 all appear 
# among the digits of the ASCII values of 'JAPH'.
sub A {
    $_[0] && do {
        ( $_[0] != $_[1] ) && shift
# skip leading garbage
# 511743 355653 344803 966723 -> 11743 55653 44803 66723
          and &A || do {
            shift;
            shift;
# skip leading garbage
# 11743 55653 44803 66723 -> 743 653 803 723
            $_ = $|;
# $| has to be 0 so don't unbuffer STDOUT
            {
                $_ *= 10;
                $_ += shift;
                $_[0] == 3 || redo
            }
# $_ = 74 65 80 72 = 'J' 'A' 'P' 'H'
            print chr, chr( 1 + 15 * shift );
# 1 + 15 * 3 = 46 = '.'
            &A;
# process next number
          }
      }
}
s,,$i++*$o+ord,ex;
# misdirection - changes $_ from 72 to 7172 (71 = 4*4+ord('7'))

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