shift, @_, Perl Begginer

sometimes I forget these differences.

sub hoge {
  my $self = @_; 

sub hoge {
  my($self) = @_;

sub hoge {
  my ($self) = @_;

First of all, show the result.

  my $self = @_;
  warn "aaaaaaaaaaaaaaaaaaaaaaa";
  warn Dumper $self;
  warn "bbbbbbbbbbbbbbbbbbbbbbb";
  my($self) = @_;
  warn Dumper $self;
  warn "ccccccccccccccccccccccc";
  my ($self) = @_;
  warn Dumper $self;

I know the result, but I could not understand the reason.

my $self = @_;
# This means Receiving Value of Array by Scalar. $self is Scalar. @_ is Array.
# $self receives the number of Elements of Array.

my($self) = @_;
# This means Receiving Value of Array by Array. ($self) is array.
# So $self receives only the 1st value of @_ as Array. 

↑↑ Then I think you should use my $self = shift.

my ($self) = @_;
# same to above.