My first attempt at perl. e^x

exp.pl

#!/usr/bin/perl -w

use strict;
use warnings;

sub calc {
    my $total = 1;
    my $ans = 10.0;
    my $x = $_[0];
    my $fac = 1.0;
    my $count = 2;

    while($ans > 0.00000000001){
        $ans = $x/$fac;
        $total += $ans;
        $x *= $_[0];
        $fac *= $count++;
    }

    return $total;
}

print "e^ ";
my $inp = <STDIN>;
my $ans = calc($inp);
print "e^x = $ans\n";