#!/usr/local/bin/perl -w

use Math::Trig qw(:pi);
# use bignum qw/e PI/;
use strict;

my $z = $ARGV[0];
die "Wrong number as argument" if ($z<=0 || $z=~/\D\D/ || !defined $z);
my $step = 1/1000000;
my $r = 0.5;
# densidad de la distribución normal estandarizada
# Z = (1/sqrt(2*pi))*exp(1)^(-0.5*z*z)
# $pi = 4*atan2(1,1);
my $static = 1/(1000000*sqrt(pi2));
my $e = exp(1);
for ( my $i = $step; $i<=$z; $i += $step ) {
    $r += $static*($e**(-$i*$i/2));
}
$r = sprintf ("%.7f",$r);
print "P[Z<=$z] = $r\n";
my $rleft = 1 - $r;
$r -= $rleft;
print "P[-$z<=Z<=$z] = $r\n";

__END__
Esta utilidad nos devuelve la probabilidad de una tabla N(0,1) de una cola
y de dos colas