Obfuscated JavaScript
Given enough time, any language will evolve into Perl.
($=(_,__=0)=>_?$(_.slice(1),+_[0]?__+(2**(_.length-1)):__):__)("10");
// --> 2
(_=$=>$<=0?1:$*_($-1))(5); // --> 120
Unobfuscate
Given enough time, any language will evolve into Perl.
($=(_,__=0)=>_?$(_.slice(1),+_[0]?__+(2**(_.length-1)):__):__)("10");
// --> 2
(_=$=>$<=0?1:$*_($-1))(5); // --> 120