#!/usr/bin/perl
use strict;
use warnings;

sub P
{
	my @r = @_;
	my $n = $#r;
	return $r[1] if $n == 1; # inferred end to recursion
	my $sum = 0;
	for my $i (1..$n)
	{
		my @r_prime = @r;
		splice(@r_prime, $n-$i+1, 1);
		$sum += ($r[$n-$i+1] - $r[$n-$i]) * P(@r_prime);
	}
	return $sum;
}

while (<DATA>)
{
	chomp;
	my @r = split(/,/, $_);
	unshift @r, 0; # sets r-naught
	print "P($_) = ", P(@r), "\n";
}
__DATA__
0.11, 0.07, 0.19
0.43, 0.31, 0.37
0.93, 0.78, 0.82
0.91, 0.12, 0.15
0.52, 0.18, 0.32