use warnings;
use strict;

use Math::Trig;

use constant PI => 3.14159265358979;

# calgary

my $lat1 = 51.32055555555556;
my $lon1 = -114.7297222222222221;

# toronto

my $lat2 = 43.65321111111111;
my $lon2 = -79.38321111111111;

my $bearing = bearing($lat1, $lon1, $lat2, $lon2);
my $direction = direction($bearing);

print "$bearing, $direction\n";

sub bearing {
    my ($lat1, $lon1, $lat2, $lon2) = map { ($_ * PI) / 180 } @_;
    my $d_lon = $lon2 - $lon1;

    my $y = sin($d_lon) * cos($lat2);
    my $x = cos($lat1) * sin($lat2) 
            - sin($lat1) 
            * cos($lat2) * cos($d_lon);

    my $rad = atan2($y, $x);
    my $deg = $rad * (180 / PI);

    return $deg < 0 ? $deg += 360 : $deg;
}
sub direction {
    my ($deg) = @_;
 
    my @directions = qw(
        N NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW N
    );
 
    my $calc = (($deg % 360) / 22.5) + .5;
 
    return $directions[$calc];
}

__END__

94.0048844699519, E