Try something as 'perl thisScript.pl 1 2 3 4 5 6 7 8 9 10' on command-line...

ObfuscatedFact.pl

use warnings;

# === Clean way: =============================== #
# use List::Util qw/ product /;                  #
# sub factorial { product 1 .. $_[0] }           #
# print factorial 5;                             #
# ============================================== #

sub{print @_,"\n"}->(sub{sub{my($c,$r)=(shift,1);;
$r=$c->($r,$_)for@_;$r}->(shift,1..shift)}->(&{sub
{sub{$_[0]*$_[1]},shift}}(shift@ARGV)))while@ARGV;

# end of script