sub new {
  my $self = shift;
  print "I was invoked by: $self\n";
}

main->new;

__output__

I was invoked by: main

##</code><code>##

{
  package demo;

  sub new {
    my($class, $foo) = @_;
    my $self         = { foo => $foo };
    return bless $self, $class;
  }
}

use Data::Dumper;
my $obj = demo->new('a string');
print Dumper($obj);

__output__

$VAR1 = bless( {
                 'foo' => 'a string'
               }, 'demo' );