in reply to Just another japh

Very, very cool. One step in particular had me going for a while... Read more for spoilers. 
# This is one big regex which sets
# $_ = ",:_,,},,],,_:){:"},,:,,,,,_,:(,:,,,(:){,,{,:,,,(,:[:){,:(:"}:"
+",:},:,,,("

s;;,:_,,},,],,_:){:"},,:,,,,,_,:(,:,,,(:){,,{,:,,,(,:[:){,:(:"}:"",:},
+:,,,(;;

# This translates individual characters, e.g., all ',' in $_ become 'P
+'.
# $_ = "PQWPPVPPTPPWQRSQXVPPQPPPPPWPQUPQPPPUQRSPPSPQPPPUPQYQRSPQUQXVQX
+XPQVPQPPPU"

y;,:_}][{"();PQWVTYSXUR;;

# This is the step that had me confused.
# It takes each individual character and xors it with 'a'. For example
+:
# a (ASCII 97) xor P (ASCII 80) is ASCII 49 ('1')
# Now $_ = "1061171151160320971101111161041011140321121011141080321040
+97099107101114"

s;(.);a^$1;eg;

# This takes each group of three and prints out their chr(); e.g., 106
+ becomes chr(106) = 'j'
# now $_ = "just another perl hacker"

s!(...)!chr$1!eg;

# Append a newline and print

$_.=$/;
print;

[download]

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Re: Re: Just another japh
by physi (Friar) on May 08, 2003 at 09:03 UTC
    Nice,
    now I know why it works :-)

    There was a problem, when I've done the tr part. In my first attempt I was using: 

    y;PQWVTYSXUR;,:_}][{}();;

    [download]
    instead of 
    y;PQWVTYSXUR;,:_}][{"();;

    [download]
    But that gaves a strange result:

    Try this little script: 

    s;;PQWPPVPPTPPWQRSQXVPPQPPPPPWPQUPQPPPUQRSPPSPQPPPUPQYQRSPQUQXVQXXPQVP
+QPPPU;;
print $_.$/;
y;PQWVTYSXUR;,:_}][{}();;
y;,:_}][{}();PQWVTYSXUR;;
print $_.$/;

    [download]
    This should normaly print out 2 equal strings. But it doesn't!? All the 'X' in the first string are replaced by a 'V'!?
    I've got no idea why!

    Cheers, physi 

    -----------------------------------
--the good, the bad and the physi--
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[reply]
[d/l]
[select]
      y;PQWVTYSXUR;,:_}][{}();;
y;,:_}][{}();PQWVTYSXUR;;

      [download]
      As you might know by now: You used } twice in your replacement string. So no wonder it fails.
[reply]
[d/l]
        8-}
        Thanks, for that hint ;-)

        -----------------------------------
--the good, the bad and the physi--
-----------------------------------
[reply]

In Section Obfuscated Code