use strict;
use warnings;
use utf8;
...
use Math::Trig;

sub geo_distance {
	my ($l1, $b1, $l2, $b2) = @_ ;

	my $rho = 180 / pi;
    my $l1_arc = $l1 / $rho;
    my $b1_arc = $b1 / $rho;
    my $l2_arc = $l2 / $rho;
    my $b2_arc = $b2 / $rho;

	# nachfolgend ist Zeile 1393
    my $e = acos(SIN(b1_arc)*sin(b2_arc) + cos(b1_arc)*cos(b2_arc)*cos(l2_arc-l1_arc));

	my $dist = $e * 6378.137;
	
	return ($dist) ;
}