#!/usr/bin/perl

use strict;
use warnings;

my ($X, $Y, $n) = @ARGV;
$n ||= 20;

my $Z = $X ** $Y;

my ($neg, $y) = ($Y < 0 ? (1, -$Y) : (0, $Y));

$y > 1 and die "Y is out of range";
my $bit = 1;
my $x = $X;
my $z = 1;
while ($y) {
    if ($y >= $bit) {
        $y -= $bit;
        $z *= $x;
    }
    $bit /= 2;
    $x = sqrt($x);
}

$z = 1/$z if $neg;
my $e = abs($z - $X ** $Y);
print "z=$z, e=$e\n";