sub exchange_words {
  # kopiere die Werte in eigene Variablen
  my ( $word1, $word2 ) = @_;

  # Woerter tauschen
  ( $word1, $word2 ) = ( $word2, $word1 );

  # gebe die veraenderten Werte zurueck
  return ( $word1, $word2 );
}

my ($hello, $world) = exchange_words( 'world!', 'hello ' );

print $hello, $world;