use Foo::Bar;

# is equivalent to:
BEGIN {
  require Foo::Bar;
  Foo::Bar->import();
};

# and with parameters:
use Foo::Bar ...;

# is equivalent to:
BEGIN {
  require Foo::Bar;
  Foo::Bar->import(...);
};

##</code><code>##

use Foo::Bar ();

# is equivalent to:
BEGIN {
  require Foo::Bar;
};

##</code><code>##

Algorithm::LUHN->import();
Algorithm::LUHN->import(qw/is_valid/);

##</code><code>##

Algorithm::LUHN->import(qw/is_valid/);

##</code><code>##

Algorithm::LUHN->import(qw/ :validity /);