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Extracting consecutive digits using regexp

I expected
regexp('ITEM 123', '.+(\d+)', 'tokens')
to return '123'. Why does it only return '3'? What would be the correct expression?

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per isakson 님의 답변 22 Jun 2019
per isakson 님이 편집함. 22 Jun 2019
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These two returns "123"
cac = regexp('ITEM 123', '.+?(\d+)', 'tokens' )
cac = regexp('ITEM 123', '[^\d]+(\d+)', 'tokens' )
First, '.+' matches anything up til the end of the text, next it gives back just as little as needed to match '(\d+)' , which is one digit.
'.+?' matches as little as needed so that '(\d+)' is able to match the following text.
I prefer '[^\d]+(\d+)'
Or why not just
cac = regexp('ITEM 123', '\d+', 'match' )

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Many thanks! For the first expression, what does the '?' character do? I've only seen it in lookaround operations, but always in the form of '?=', '?<=' etc. and never by itself.
Search Quantifiers and Lazy on the page Regular Expressions

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