Depending on the parts you have already written and the functionality you need, Mozilla::PublicSuffix might help you to determine what is "a domain" and what is "a hostname in a domain".

If your question is only about string manipulation, have you considered using split on a dot and taking the first result?

    my @parts = split /\./, $input;

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In reply to Re: Steps to get a substring from a string by Corion
in thread Steps to get a substring from a string by shroh

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