If you don't mind changing the calling conventions of your subroutine, go a step further and use named arguments in the form of a hash:

sub someFunc {
   my %args = @_;
   my @arglist = qw{ client_number MM DD S };
   foreach (@arglist) {
      die "$_ not given" unless exists $args{$_};
   }

   # Now use $args{client_number} and $args{MM}
}
[download]