[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__