Read the hang

Here is a pattern with the shape that hangs. Before running it, say which of these inputs it matches — and bear in mind that one of them is the reason this task exists.

^(?:\w+\s?)+$

^(?:\w+\s?)+$

^+$

^(?:\w+\s?)+$

^(?:)+$

^(?:+?)+$

Your prediction

One row per input: whether it matches, and what each group captures
Input	Matches?
one two
one
one two three
one two!
(empty)

Nothing runs until you have answered every row.