Actually it is complaining about $my_html_return - you didn't inititalise this variable. Replace it with

$my_html_return .= $_;
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And you'll lose that warning. Perl is just telling you where the error is in the current file (in this case a socket) in the error message "Use of uninitialized value at ./gethtml.pl line 16, <my_socket> chunk +1." just in case that helps you debug the problem (which it does sometimes).

The error is nothing to do with the socket.