Perl subroutines

[Paul Mooring]

I'm working on a perl script, and I have a lot more experience in ruby
than I do in perl.  As far as I can tell there is no way to explicitly
define arguments for a subroutine in perl, for example

sub addNums(number1, number2) {
  sum = number1 + number2;

  return sum;
}

rather than

sub addNums {
  number1 = shift;
  number2 = shift;
  sum = number1 + number2;

  return sum;
}

is there anyway to do this, and if not does anyone have some advice on
a way to make this a bit more readable in perl?