linux - Decrypt obfuscated perl script

Question

Had some spam issues on my server and, after finding out and removing some Perl and PHP scripts I'm down to checking what they really do, although I'm a senior PHP programmer I have little experience with Perl, can anyone give me a hand with the script here:

http://pastebin.com/MKiN8ifp

(It was one long line of code, script was called list.pl)

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The start of the script is:

$??s:;s:s;;$?::s;(.*); ]="&\%[=.*.,-))'-,-#-*.).<.'.+-<-~-#,~-.-,.+,~-{-,.<'`.{'`'<-<--):)++,+#,-.{).+,,~+{+,,<)..})<.{.)-,.+.,.)-#):)++,+#,-.{).+,,~+{+,,<)..})<*{.}'`'<-<--):)++,+#,-.{).+:,+,+,',~+*+~+~+{+<+,)..})<'`'<.{'`'<'<-}.<)'+'.:*}.*.'-|-<.+):)~*{)~)|)++,+#,-.{).+:,+,+,',~+*+~+~+{+<+,)..})

It continues with precious few non-punctuation characters until the very end:

0-9;\_rs}&a-h;;s;(.*);$_;see;

Answer 1

Replace the s;(.*);$_;see; with print to get this. Replace s;(.*);$_;see; again with print in the first half of the payload to get this, which is the decryption code. The second half of the payload is the code to decrypt, but I can't go any further with it, because as you see, the decryption code is looking for a key in an envvar or a cookie (so that only the script's creator can control it or decode it, presumably), and I don't have that key. This is actually reasonably cleverly done.