(?:) is a non-capturing group, which groups multiple tokes together without
creating a capture group

In my case,
(?:\.) 
means, search for a DOT as group subpattern, but don't capture it

For details see the following article
[url]https://stackoverflow.com/questions/3512471/what-is-a-non-capturing-group-w
hat-does-do[/url]

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