Vim: Searching and Replace regex fails

Content:

1.                  Text is here.
20.                 More text.

Why d开发者_C百科oes this Vim search and replace string fail?

:%s/^\d+\.\s+/# /g

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Some metacharacters need to be escaped in order to take effect:

:%s/^\d\+\.\s\+/# /g

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The + must be escaped in Vim's version of regex. So use \+.