In a moment or two he was back. 
( ( In ( ( ( a moment ) or ) two ) ) ( he ( ( was back ) . ) ) )
(ROOT (S (PP (IN In) (NP (NP (DT a) (NN moment)) (CC or) (NP (CD two)))) (NP (PRP he)) (VP (VBD was) (ADVP (RB back))) (. .)))
While he was gone, I spent some time observing the room. 
( ( While ( he ( was gone ) ) ) ( , ( I ( ( ( spent ( some time ) ) ( observing ( the room ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN While) (S (NP (PRP he)) (VP (VBD was) (VP (VBN gone))))) (, ,) (NP (PRP I)) (VP (VBD spent) (NP (DT some) (NN time)) (S (VP (VBG observing) (NP (DT the) (NN room))))) (. .)))