... other Tk code 
my $timer = $mw->repeat(10, \&read_it );
MainLoop;

sub read_it{
   my $client = $listen->accept or die "Accept failed: $!";
   if( IO::Select->new($client)->can_read(5) ) {
      sysread( $client, $_, 1 ) and print;
   } else {   print "Timeout\n";
   } close $client;
}