There's no difference in declaring a method and a subroutine. The only difference is how you call methods and what arguments they get.

sub some_function
{
   my ($first, $second) = @_;

   ...
}

sub some_method
{
   my ($self, $first, $second) = @_;

   ...
}
[download]

You need to call a method with a class name or an object:

SomeClass->some_method( $first, $second );

$some_object->some_method( $first, $second );
[download]

To create an object, call a constructor (a method called with a class name). A constructor uses the bless operator to associate a reference with a class name:

package SomeClass;

sub new
{
    my $class = shift;
    bless {}, $class;
}

...

my $some_object = SomeClass->new();
[download]