There is more than one way to do it. You could add double quotes via additional search and replace.

perl -pi.back -e 's#\D*(\d{3})\D*(\d{3})\D*(\d{4})#(${1}) ${2}-${3}#s;
+ s#^#""; s#$#"#' clients.txt

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In reply to Re^3: Running complex sed from perl by wazat
in thread Running complex sed from perl by sunglant

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