my $num1 = 150;
my $num2 = 1000;

# set which is biggest and which smallest
my $max = ($num1 > $num2)? $num1 : $num2;
my $min = ($num1 < $num2)? $num1 : $num2;

for $divisor (reverse 0 .. $min) {
    # fail unless our divisor divides evenly into $min
    next if $min % $divisor;
    # fail unless our divisor divides evenly into $max
    next if $max % $divisor;
    print "Largest common divisor is $divisor\n";
  last;
}