[mylibrary1.pl]

sub half {
   my $number = shift;
   return $number / 2;
}

##</code><code>##

[mylibrary1.pm]

package mylibrary1;

use base 'Exporter';
use vars qw( @EXPORT @EXPORT_OK );

@EXPORT = qw( half ); # These are the ones that are imported if nothing is specified.
@EXPORT_OK = qw( half ); # These are the ones you may specify, if you want.

sub half {
   my $number = shift;
   return $number / 2;
}

1; # All .pm files must end with a true value
__END__

##</code><code>##

[myscript.pl]

require 'mylibrary1.pl';

print half( 10 ), "\n";

##</code><code>##

[myscript.pl]

use mylibrary1 qw( half );

print half( 10 ), "\n";

##</code><code>##

use Foo; # Imports everything in @EXPORT, nothing in @EXPORT_OK

use Foo 'bar'; # Imports 'bar' if it's in @EXPORT_OK. Imports nothing from @EXPORT

use Foo (); # Imports NOTHING from either.