Further to shmem's post:

sub _ss {
  my ($self, %arg) = @_;

  print Dumper(\%arg);
}
[download]

... so what you probably want is something like:

sub _ss {
  my ($self, $hashref) = @_;

  print Dumper($hashref);

  # do stuff with $hashref

}
[download]

or maybe:

sub _ss {
  my ($self, $hashref) = @_;

  my %hash = %$hashref;

  print Dumper(\%hash);

  # do stuff with %hash

}
[download]