You can make the last one even more useless..

sub p {
    return (map { $a ? ($a *= $_) : ($a = 1) } (($_[0] - $_[1] + 1) ..
+ $_[0]))[-1];
}
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The little ?: operator is great for making code unreadable :)

For those of you who are not familiar with ?: it is the 'conditional operator' and can be found in the perlop pages.