#!perl -l
use strict;
use warnings;

# Return the array, with the first and Nth elements swapped
sub swapcar {
    my ($arr, $n, $between) = @_;
    return (@$between, @$arr) if (@$arr <= 1 or $n == 0);
    my ($car1, $car2, @cdr) = @$arr;
    return (($n == 1)
           ? ($car2, @$between, $car1, @cdr)
           : swapcar([$car1, @cdr], $n-1, [@$between, $car2])
    );
}

sub FY_tail {
  my ($car, @cdr) = @_;
  return unless @cdr;
  ($car, functional_FY(@cdr));
}

sub functional_FY {
  my ($car, @cdr) = @_;
  return @cdr ? FY_tail(swapcar([@_], int rand @_, [])) : ($car);
}

print join ', ', functional_FY(my @foo = qw(a k q j 10)) for (1..5);