ISBN2 by flagitious

#!ruby -p
$_[j= ~/\?/]=?0
$_[j]+=1until(X=10)>eval([scan(/\d|X/),i=0]*'*($_[17]?33-i=22-i:i-=X)+')%?n

Note that non-ascii characters in the above source code will be escaped (such as \x9f).

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