"Test.pl" 

#use lib "./Nzd/";  ->not sure if this should be here
#push @INC, "./Nzd/"; ->not sure if this should be here
use strict;
use warnings;

use Nzd::NZD;   #Nzd is a directory containing NZD.pm

my ($x,$y)= (8,36);

my $t=NZD($x,$y);
my $c=$x/$t;
my $g=$y/$t;

print "\nc= $c,  g= $g";


------------------------------------

"NZD.pm"

package Nzd::NZD;

use strict;
sub NZD {
  my ($x, $b) = @_;
   if ($x > $b){
   	($x,$b) = ($b,$x);
  }
  while ($x) {
    ($x, $b) = ($b % $x, $x);
  }
  return $b;
}
1;