Edit:Peguei o genérico. Muito simples no final (mas demorei um pouco para chegar lá)
WITH words AS
( SELECT REGEXP_SUBSTR( '&txt', '\S+', 1, LEVEL ) AS word
, LEVEL AS num
FROM DUAL
CONNECT BY LEVEL <= LENGTH( REGEXP_REPLACE( '&txt', '\S+\s*', 'X' ) )
)
SELECT SYS_CONNECT_BY_PATH( W.word, ' ' )
FROM words W
CONNECT BY NOCYCLE PRIOR W.num != W.num
Edit2:Removidas coisas redundantes de maxnum. Restos de tentativas anteriores
