Try this instead, in case the select method returns a reference to an array:

my $rhSet = IO::Select->select($readSet, undef, undef, 0);
foreach $rh(@$rhSet)
{
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You should also read the perldoc for IO::Select, there is a short example at the end.

perldoc IO::Select

EXAMPLE
     Here is a short example which shows how "IO::Select" could
     be used to write a server which communicates with several
     sockets while also listening for more connections on a
     listen socket

         use IO::Select;
         use IO::Socket;

         $lsn = new IO::Socket::INET(Listen => 1, LocalPort => 8080);
         $sel = new IO::Select( $lsn );
         while(@ready = $sel->can_read) {
             foreach $fh (@ready) {
                 if($fh == $lsn) {
                     # Create a new socket
                     $new = $lsn->accept;
                     $sel->add($new);
                 }
                 else {
                     # Process socket

                     # Maybe we have finished with the socket
                     $sel->remove($fh);
                     $fh->close;
                 }
             }
         }
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